| Message ID | 20220527073422.367910-1-contact@emersion.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] dma-buf: Add a capabilities directory | expand |
Am 27.05.22 um 09:34 schrieb Simon Ser: > To discover support for new DMA-BUF IOCTLs, user-space has no > choice but to try to perform the IOCTL on an existing DMA-BUF. > However, user-space may want to figure out whether or not the > IOCTL is available before it has a DMA-BUF at hand, e.g. at > initialization time in a Wayland compositor. > > Add a /sys/kernel/dmabuf/caps directory which allows the DMA-BUF > subsystem to advertise supported features. Add a > sync_file_import_export entry which indicates that importing and > exporting sync_files from/to DMA-BUFs is supported. I find a separate directory rather unusual, but can't come up with any better idea either. IIRC the security module had a mask file with names for the supported capabilities. > > v2: Add missing files lost in a rebase > > v3: > - Create separate file in Documentation/ABI/testing/, add it to > MAINTAINERS > - Fix kernel version (Daniel) > - Remove unnecessary brackets (Jason) > - Fix SPDX comment style > > Signed-off-by: Simon Ser <contact@emersion.fr> > Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch> > Cc: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl> > Cc: Christian König <christian.koenig@amd.com> > Cc: Greg KH <greg@kroah.com> > --- > .../ABI/testing/sysfs-kernel-dmabuf-caps | 13 +++++ > MAINTAINERS | 1 + > drivers/dma-buf/Makefile | 2 +- > drivers/dma-buf/dma-buf-sysfs-caps.c | 51 +++++++++++++++++++ > drivers/dma-buf/dma-buf-sysfs-caps.h | 16 ++++++ > drivers/dma-buf/dma-buf-sysfs-stats.c | 16 ++---- > drivers/dma-buf/dma-buf-sysfs-stats.h | 6 ++- > drivers/dma-buf/dma-buf.c | 43 ++++++++++++++-- > include/uapi/linux/dma-buf.h | 6 +++ > 9 files changed, 134 insertions(+), 20 deletions(-) > create mode 100644 Documentation/ABI/testing/sysfs-kernel-dmabuf-caps > create mode 100644 drivers/dma-buf/dma-buf-sysfs-caps.c > create mode 100644 drivers/dma-buf/dma-buf-sysfs-caps.h > > diff --git a/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps b/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps > new file mode 100644 > index 000000000000..f83af422fd18 > --- /dev/null > +++ b/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps > @@ -0,0 +1,13 @@ > +What: /sys/kernel/dmabuf/caps > +Date: May 2022 > +KernelVersion: v5.20 > +Contact: Simon Ser <contact@emersion.fr> > +Description: This directory advertises DMA-BUF capabilities supported by the > + kernel. > + > +What: /sys/kernel/dmabuf/caps/sync_file_import_export > +Date: May 2022 > +KernelVersion: v5.20 > +Contact: Simon Ser <contact@emersion.fr> > +Description: This file is read-only and advertises support for importing and > + exporting sync_files from/to DMA-BUFs. > diff --git a/MAINTAINERS b/MAINTAINERS > index 11da16bfa123..8966686f7231 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -5871,6 +5871,7 @@ L: dri-devel@lists.freedesktop.org > L: linaro-mm-sig@lists.linaro.org (moderated for non-subscribers) > S: Maintained > T: git git://anongit.freedesktop.org/drm/drm-misc > +F: Documentation/ABI/testing/sysfs-kernel-dmabuf-caps > F: Documentation/driver-api/dma-buf.rst > F: drivers/dma-buf/ > F: include/linux/*fence.h > diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile > index 4c9eb53ba3f8..afc874272710 100644 > --- a/drivers/dma-buf/Makefile > +++ b/drivers/dma-buf/Makefile > @@ -1,6 +1,6 @@ > # SPDX-License-Identifier: GPL-2.0-only > obj-y := dma-buf.o dma-fence.o dma-fence-array.o dma-fence-chain.o \ > - dma-resv.o > + dma-resv.o dma-buf-sysfs-caps.o > obj-$(CONFIG_DMABUF_HEAPS) += dma-heap.o > obj-$(CONFIG_DMABUF_HEAPS) += heaps/ > obj-$(CONFIG_SYNC_FILE) += sync_file.o > diff --git a/drivers/dma-buf/dma-buf-sysfs-caps.c b/drivers/dma-buf/dma-buf-sysfs-caps.c > new file mode 100644 > index 000000000000..82b91eb874a9 > --- /dev/null > +++ b/drivers/dma-buf/dma-buf-sysfs-caps.c > @@ -0,0 +1,51 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * DMA-BUF sysfs capabilities. > + * > + * Copyright (C) 2022 Simon Ser > + */ > + > +#include <linux/kobject.h> > +#include <linux/sysfs.h> > + > +#include "dma-buf-sysfs-caps.h" > + > +static ssize_t sync_file_import_export_show(struct kobject *kobj, > + struct kobj_attribute *attr, > + char *buf) > +{ > + return sysfs_emit(buf, "1\n"); > +} > + > +static struct kobj_attribute dma_buf_sync_file_import_export_attr = > + __ATTR_RO(sync_file_import_export); > + > +static struct attribute *dma_buf_caps_attrs[] = { > + &dma_buf_sync_file_import_export_attr.attr, > + NULL, > +}; > + > +static const struct attribute_group dma_buf_caps_attr_group = { > + .attrs = dma_buf_caps_attrs, > +}; Didn't we had macros for those? I think I have seen something for that. Apart from those two random thoughts looks good to me as well. Regards, Christian. > + > +static struct kobject *dma_buf_caps_kobj; > + > +int dma_buf_init_sysfs_capabilities(struct kset *kset) > +{ > + int ret; > + > + dma_buf_caps_kobj = kobject_create_and_add("caps", &kset->kobj); > + if (!dma_buf_caps_kobj) > + return -ENOMEM; > + > + ret = sysfs_create_group(dma_buf_caps_kobj, &dma_buf_caps_attr_group); > + if (ret) > + kobject_put(dma_buf_caps_kobj); > + return ret; > +} > + > +void dma_buf_uninit_sysfs_capabilities(void) > +{ > + kobject_put(dma_buf_caps_kobj); > +} > diff --git a/drivers/dma-buf/dma-buf-sysfs-caps.h b/drivers/dma-buf/dma-buf-sysfs-caps.h > new file mode 100644 > index 000000000000..d7bcef490b31 > --- /dev/null > +++ b/drivers/dma-buf/dma-buf-sysfs-caps.h > @@ -0,0 +1,16 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * DMA-BUF sysfs capabilities. > + * > + * Copyright (C) 2022 Simon Ser > + */ > + > +#ifndef _DMA_BUF_SYSFS_CAPS_H > +#define _DMA_BUF_SYSFS_CAPS_H > + > +struct kset; > + > +int dma_buf_init_sysfs_capabilities(struct kset *kset); > +void dma_buf_uninit_sysfs_capabilities(void); > + > +#endif // _DMA_BUF_SYSFS_CAPS_H > diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c b/drivers/dma-buf/dma-buf-sysfs-stats.c > index 2bba0babcb62..e2e62f83ce18 100644 > --- a/drivers/dma-buf/dma-buf-sysfs-stats.c > +++ b/drivers/dma-buf/dma-buf-sysfs-stats.c > @@ -141,23 +141,14 @@ static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = { > .filter = dmabuf_sysfs_uevent_filter, > }; > > -static struct kset *dma_buf_stats_kset; > static struct kset *dma_buf_per_buffer_stats_kset; > -int dma_buf_init_sysfs_statistics(void) > +int dma_buf_init_sysfs_statistics(struct kset *kset) > { > - dma_buf_stats_kset = kset_create_and_add("dmabuf", > - &dmabuf_sysfs_no_uevent_ops, > - kernel_kobj); > - if (!dma_buf_stats_kset) > - return -ENOMEM; > - > dma_buf_per_buffer_stats_kset = kset_create_and_add("buffers", > &dmabuf_sysfs_no_uevent_ops, > - &dma_buf_stats_kset->kobj); > - if (!dma_buf_per_buffer_stats_kset) { > - kset_unregister(dma_buf_stats_kset); > + &kset->kobj); > + if (!dma_buf_per_buffer_stats_kset) > return -ENOMEM; > - } > > return 0; > } > @@ -165,7 +156,6 @@ int dma_buf_init_sysfs_statistics(void) > void dma_buf_uninit_sysfs_statistics(void) > { > kset_unregister(dma_buf_per_buffer_stats_kset); > - kset_unregister(dma_buf_stats_kset); > } > > int dma_buf_stats_setup(struct dma_buf *dmabuf) > diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.h b/drivers/dma-buf/dma-buf-sysfs-stats.h > index a49c6e2650cc..798c54fb8ee3 100644 > --- a/drivers/dma-buf/dma-buf-sysfs-stats.h > +++ b/drivers/dma-buf/dma-buf-sysfs-stats.h > @@ -8,9 +8,11 @@ > #ifndef _DMA_BUF_SYSFS_STATS_H > #define _DMA_BUF_SYSFS_STATS_H > > +struct kset; > + > #ifdef CONFIG_DMABUF_SYSFS_STATS > > -int dma_buf_init_sysfs_statistics(void); > +int dma_buf_init_sysfs_statistics(struct kset *kset); > void dma_buf_uninit_sysfs_statistics(void); > > int dma_buf_stats_setup(struct dma_buf *dmabuf); > @@ -18,7 +20,7 @@ int dma_buf_stats_setup(struct dma_buf *dmabuf); > void dma_buf_stats_teardown(struct dma_buf *dmabuf); > #else > > -static inline int dma_buf_init_sysfs_statistics(void) > +static inline int dma_buf_init_sysfs_statistics(struct kset *kset) > { > return 0; > } > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index 5e1b0534b3ce..b5c5a5050508 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c > @@ -30,6 +30,7 @@ > #include <uapi/linux/dma-buf.h> > #include <uapi/linux/magic.h> > > +#include "dma-buf-sysfs-caps.h" > #include "dma-buf-sysfs-stats.h" > > static inline int is_dma_buf_file(struct file *); > @@ -1546,22 +1547,54 @@ static inline void dma_buf_uninit_debugfs(void) > } > #endif > > +/* Capabilities and statistics files do not need to send uevents. */ > +static int dmabuf_sysfs_uevent_filter(struct kobject *kobj) > +{ > + return 0; > +} > + > +static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = { > + .filter = dmabuf_sysfs_uevent_filter, > +}; > + > +static struct kset *dma_buf_kset; > + > static int __init dma_buf_init(void) > { > int ret; > > - ret = dma_buf_init_sysfs_statistics(); > + dma_buf_kset = kset_create_and_add("dmabuf", > + &dmabuf_sysfs_no_uevent_ops, > + kernel_kobj); > + if (!dma_buf_kset) > + return -ENOMEM; > + > + ret = dma_buf_init_sysfs_capabilities(dma_buf_kset); > if (ret) > - return ret; > + goto err_kset; > + > + ret = dma_buf_init_sysfs_statistics(dma_buf_kset); > + if (ret) > + goto err_sysfs_caps; > > dma_buf_mnt = kern_mount(&dma_buf_fs_type); > - if (IS_ERR(dma_buf_mnt)) > - return PTR_ERR(dma_buf_mnt); > + if (IS_ERR(dma_buf_mnt)) { > + ret = PTR_ERR(dma_buf_mnt); > + goto err_sysfs_stats; > + } > > mutex_init(&db_list.lock); > INIT_LIST_HEAD(&db_list.head); > dma_buf_init_debugfs(); > return 0; > + > +err_sysfs_stats: > + dma_buf_uninit_sysfs_statistics(); > +err_sysfs_caps: > + dma_buf_uninit_sysfs_capabilities(); > +err_kset: > + kset_unregister(dma_buf_kset); > + return ret; > } > subsys_initcall(dma_buf_init); > > @@ -1570,5 +1603,7 @@ static void __exit dma_buf_deinit(void) > dma_buf_uninit_debugfs(); > kern_unmount(dma_buf_mnt); > dma_buf_uninit_sysfs_statistics(); > + dma_buf_uninit_sysfs_capabilities(); > + kset_unregister(dma_buf_kset); > } > __exitcall(dma_buf_deinit); > diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h > index 70e213a0d7d9..ab3afd5da75a 100644 > --- a/include/uapi/linux/dma-buf.h > +++ b/include/uapi/linux/dma-buf.h > @@ -114,6 +114,9 @@ struct dma_buf_sync { > * ordering via these fences, it is the respnosibility of userspace to use > * locks or other mechanisms to ensure that no other context adds fences or > * submits work between steps 1 and 3 above. > + * > + * Userspace can check the availability of this API via > + * /sys/kernel/dmabuf/caps/sync_file_import_export. > */ > struct dma_buf_export_sync_file { > /** > @@ -146,6 +149,9 @@ struct dma_buf_export_sync_file { > * synchronized APIs such as Vulkan to inter-op with dma-buf consumers > * which expect implicit synchronization such as OpenGL or most media > * drivers/video. > + * > + * Userspace can check the availability of this API via > + * /sys/kernel/dmabuf/caps/sync_file_import_export. > */ > struct dma_buf_import_sync_file { > /**
On Mon, May 30, 2022 at 09:09:30AM +0200, Christian König wrote: > Am 27.05.22 um 09:34 schrieb Simon Ser: > > To discover support for new DMA-BUF IOCTLs, user-space has no > > choice but to try to perform the IOCTL on an existing DMA-BUF. > > However, user-space may want to figure out whether or not the > > IOCTL is available before it has a DMA-BUF at hand, e.g. at > > initialization time in a Wayland compositor. > > > > Add a /sys/kernel/dmabuf/caps directory which allows the DMA-BUF > > subsystem to advertise supported features. Add a > > sync_file_import_export entry which indicates that importing and > > exporting sync_files from/to DMA-BUFs is supported. > > I find a separate directory rather unusual, but can't come up with any > better idea either. > > IIRC the security module had a mask file with names for the supported > capabilities. > > > > > v2: Add missing files lost in a rebase > > > > v3: > > - Create separate file in Documentation/ABI/testing/, add it to > > MAINTAINERS > > - Fix kernel version (Daniel) > > - Remove unnecessary brackets (Jason) > > - Fix SPDX comment style > > > > Signed-off-by: Simon Ser <contact@emersion.fr> > > Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com> > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch> > > Cc: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl> > > Cc: Christian König <christian.koenig@amd.com> > > Cc: Greg KH <greg@kroah.com> > > --- > > .../ABI/testing/sysfs-kernel-dmabuf-caps | 13 +++++ > > MAINTAINERS | 1 + > > drivers/dma-buf/Makefile | 2 +- > > drivers/dma-buf/dma-buf-sysfs-caps.c | 51 +++++++++++++++++++ > > drivers/dma-buf/dma-buf-sysfs-caps.h | 16 ++++++ > > drivers/dma-buf/dma-buf-sysfs-stats.c | 16 ++---- > > drivers/dma-buf/dma-buf-sysfs-stats.h | 6 ++- > > drivers/dma-buf/dma-buf.c | 43 ++++++++++++++-- > > include/uapi/linux/dma-buf.h | 6 +++ > > 9 files changed, 134 insertions(+), 20 deletions(-) > > create mode 100644 Documentation/ABI/testing/sysfs-kernel-dmabuf-caps > > create mode 100644 drivers/dma-buf/dma-buf-sysfs-caps.c > > create mode 100644 drivers/dma-buf/dma-buf-sysfs-caps.h > > > > diff --git a/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps b/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps > > new file mode 100644 > > index 000000000000..f83af422fd18 > > --- /dev/null > > +++ b/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps > > @@ -0,0 +1,13 @@ > > +What: /sys/kernel/dmabuf/caps > > +Date: May 2022 > > +KernelVersion: v5.20 > > +Contact: Simon Ser <contact@emersion.fr> > > +Description: This directory advertises DMA-BUF capabilities supported by the > > + kernel. > > + > > +What: /sys/kernel/dmabuf/caps/sync_file_import_export > > +Date: May 2022 > > +KernelVersion: v5.20 > > +Contact: Simon Ser <contact@emersion.fr> > > +Description: This file is read-only and advertises support for importing and > > + exporting sync_files from/to DMA-BUFs. > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 11da16bfa123..8966686f7231 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -5871,6 +5871,7 @@ L: dri-devel@lists.freedesktop.org > > L: linaro-mm-sig@lists.linaro.org (moderated for non-subscribers) > > S: Maintained > > T: git git://anongit.freedesktop.org/drm/drm-misc > > +F: Documentation/ABI/testing/sysfs-kernel-dmabuf-caps > > F: Documentation/driver-api/dma-buf.rst > > F: drivers/dma-buf/ > > F: include/linux/*fence.h > > diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile > > index 4c9eb53ba3f8..afc874272710 100644 > > --- a/drivers/dma-buf/Makefile > > +++ b/drivers/dma-buf/Makefile > > @@ -1,6 +1,6 @@ > > # SPDX-License-Identifier: GPL-2.0-only > > obj-y := dma-buf.o dma-fence.o dma-fence-array.o dma-fence-chain.o \ > > - dma-resv.o > > + dma-resv.o dma-buf-sysfs-caps.o > > obj-$(CONFIG_DMABUF_HEAPS) += dma-heap.o > > obj-$(CONFIG_DMABUF_HEAPS) += heaps/ > > obj-$(CONFIG_SYNC_FILE) += sync_file.o > > diff --git a/drivers/dma-buf/dma-buf-sysfs-caps.c b/drivers/dma-buf/dma-buf-sysfs-caps.c > > new file mode 100644 > > index 000000000000..82b91eb874a9 > > --- /dev/null > > +++ b/drivers/dma-buf/dma-buf-sysfs-caps.c > > @@ -0,0 +1,51 @@ > > +// SPDX-License-Identifier: GPL-2.0-only > > +/* > > + * DMA-BUF sysfs capabilities. > > + * > > + * Copyright (C) 2022 Simon Ser > > + */ > > + > > +#include <linux/kobject.h> > > +#include <linux/sysfs.h> > > + > > +#include "dma-buf-sysfs-caps.h" > > + > > +static ssize_t sync_file_import_export_show(struct kobject *kobj, > > + struct kobj_attribute *attr, > > + char *buf) > > +{ > > + return sysfs_emit(buf, "1\n"); > > +} > > + > > +static struct kobj_attribute dma_buf_sync_file_import_export_attr = > > + __ATTR_RO(sync_file_import_export); > > + > > +static struct attribute *dma_buf_caps_attrs[] = { > > + &dma_buf_sync_file_import_export_attr.attr, > > + NULL, > > +}; > > + > > +static const struct attribute_group dma_buf_caps_attr_group = { > > + .attrs = dma_buf_caps_attrs, > > +}; > > Didn't we had macros for those? I think I have seen something for that. Yes, please use ATTRIBUTE_GROUPS() > > + > > +static struct kobject *dma_buf_caps_kobj; > > + > > +int dma_buf_init_sysfs_capabilities(struct kset *kset) > > +{ > > + int ret; > > + > > + dma_buf_caps_kobj = kobject_create_and_add("caps", &kset->kobj); > > + if (!dma_buf_caps_kobj) > > + return -ENOMEM; > > + > > + ret = sysfs_create_group(dma_buf_caps_kobj, &dma_buf_caps_attr_group); Why do we have "raw" kobjects here? A group can have a name, which puts it in the subdirectory of the object it is attached to. Please do that and do not create a new kobject. thanks, greg k-h
On Monday, May 30th, 2022 at 09:09, Christian König <christian.koenig@amd.com> wrote: > I find a separate directory rather unusual, but can't come up with any > better idea either. > > IIRC the security module had a mask file with names for the supported > capabilities. Are you referring to /sys/kernel/security/lsm? This sounds more painful to parse from user-space. Instead of a simple stat(), user-space would need to read the file, split on commas, and compare strings.
On Monday, May 30th, 2022 at 09:20, Greg KH <gregkh@linuxfoundation.org> wrote: > > > +static struct attribute *dma_buf_caps_attrs[] = { > > > + &dma_buf_sync_file_import_export_attr.attr, > > > + NULL, > > > +}; > > > + > > > +static const struct attribute_group dma_buf_caps_attr_group = { > > > + .attrs = dma_buf_caps_attrs, > > > +}; > > > > Didn't we had macros for those? I think I have seen something for that. > > Yes, please use ATTRIBUTE_GROUPS() This doesn't allow the user to set a group name, and creates an unused "_groups" variable, causing warnings. > > > + > > > +static struct kobject *dma_buf_caps_kobj; > > > + > > > +int dma_buf_init_sysfs_capabilities(struct kset *kset) > > > +{ > > > + int ret; > > > + > > > + dma_buf_caps_kobj = kobject_create_and_add("caps", &kset->kobj); > > > + if (!dma_buf_caps_kobj) > > > + return -ENOMEM; > > > + > > > + ret = sysfs_create_group(dma_buf_caps_kobj, &dma_buf_caps_attr_group); > > Why do we have "raw" kobjects here? > > A group can have a name, which puts it in the subdirectory of the object > it is attached to. Please do that and do not create a new kobject. I see, I'll switch to sysfs_create_group with a group name in the next version. Thanks for the pointers!
On Mon, May 30, 2022 at 08:15:04AM +0000, Simon Ser wrote: > On Monday, May 30th, 2022 at 09:20, Greg KH <gregkh@linuxfoundation.org> wrote: > > > > > +static struct attribute *dma_buf_caps_attrs[] = { > > > > + &dma_buf_sync_file_import_export_attr.attr, > > > > + NULL, > > > > +}; > > > > + > > > > +static const struct attribute_group dma_buf_caps_attr_group = { > > > > + .attrs = dma_buf_caps_attrs, > > > > +}; > > > > > > Didn't we had macros for those? I think I have seen something for that. > > > > Yes, please use ATTRIBUTE_GROUPS() > > This doesn't allow the user to set a group name, and creates an unused > "_groups" variable, causing warnings. Then set a group name. But you really want to almost always be using lists of groups, which is why that macro works that way. > > > > > + > > > > +static struct kobject *dma_buf_caps_kobj; > > > > + > > > > +int dma_buf_init_sysfs_capabilities(struct kset *kset) > > > > +{ > > > > + int ret; > > > > + > > > > + dma_buf_caps_kobj = kobject_create_and_add("caps", &kset->kobj); > > > > + if (!dma_buf_caps_kobj) > > > > + return -ENOMEM; > > > > + > > > > + ret = sysfs_create_group(dma_buf_caps_kobj, &dma_buf_caps_attr_group); > > > > Why do we have "raw" kobjects here? > > > > A group can have a name, which puts it in the subdirectory of the object > > it is attached to. Please do that and do not create a new kobject. > > I see, I'll switch to sysfs_create_group with a group name in the next version. No, do not do that, add it to the list of groups for the original kobject. thanks, greg k-h
On Mon, 2022-05-30 at 10:26 +0200, Greg KH wrote: > On Mon, May 30, 2022 at 08:15:04AM +0000, Simon Ser wrote: > > On Monday, May 30th, 2022 at 09:20, Greg KH > > <gregkh@linuxfoundation.org> wrote: > > > > > > > +static struct attribute *dma_buf_caps_attrs[] = { > > > > > + &dma_buf_sync_file_import_export_attr.attr, > > > > > + NULL, > > > > > +}; > > > > > + > > > > > +static const struct attribute_group dma_buf_caps_attr_group > > > > > = { > > > > > + .attrs = dma_buf_caps_attrs, > > > > > +}; > > > > > > > > Didn't we had macros for those? I think I have seen something > > > > for that. > > > > > > Yes, please use ATTRIBUTE_GROUPS() > > > > This doesn't allow the user to set a group name, and creates an > > unused > > "_groups" variable, causing warnings. > > Then set a group name. > > But you really want to almost always be using lists of groups, which > is > why that macro works that way. I think I see the confusion here. The ATTRIBUTE_GROUPS() macro is intended for device drivers and to be used with add_device(). However, this is dma-buf so there is no device and no add_device() call to hook. Unless there are other magic macros to use in this case, I think we're stuck doing it manually. --Jason > > > > > > > + > > > > > +static struct kobject *dma_buf_caps_kobj; > > > > > + > > > > > +int dma_buf_init_sysfs_capabilities(struct kset *kset) > > > > > +{ > > > > > + int ret; > > > > > + > > > > > + dma_buf_caps_kobj = kobject_create_and_add("caps", > > > > > &kset->kobj); > > > > > + if (!dma_buf_caps_kobj) > > > > > + return -ENOMEM; > > > > > + > > > > > + ret = sysfs_create_group(dma_buf_caps_kobj, > > > > > &dma_buf_caps_attr_group); > > > > > > Why do we have "raw" kobjects here? > > > > > > A group can have a name, which puts it in the subdirectory of the > > > object > > > it is attached to. Please do that and do not create a new > > > kobject. > > > > I see, I'll switch to sysfs_create_group with a group name in the > > next version. > > No, do not do that, add it to the list of groups for the original > kobject. > > thanks, > > greg k-h
On Tue, May 31, 2022 at 07:53:50AM -0500, Jason Ekstrand wrote: > On Mon, 2022-05-30 at 10:26 +0200, Greg KH wrote: > > On Mon, May 30, 2022 at 08:15:04AM +0000, Simon Ser wrote: > > > On Monday, May 30th, 2022 at 09:20, Greg KH > > > <gregkh@linuxfoundation.org> wrote: > > > > > > > > > +static struct attribute *dma_buf_caps_attrs[] = { > > > > > > + &dma_buf_sync_file_import_export_attr.attr, > > > > > > + NULL, > > > > > > +}; > > > > > > + > > > > > > +static const struct attribute_group dma_buf_caps_attr_group > > > > > > = { > > > > > > + .attrs = dma_buf_caps_attrs, > > > > > > +}; > > > > > > > > > > Didn't we had macros for those? I think I have seen something > > > > > for that. > > > > > > > > Yes, please use ATTRIBUTE_GROUPS() > > > > > > This doesn't allow the user to set a group name, and creates an > > > unused > > > "_groups" variable, causing warnings. > > > > Then set a group name. > > > > But you really want to almost always be using lists of groups, which > > is > > why that macro works that way. > > I think I see the confusion here. The ATTRIBUTE_GROUPS() macro is > intended for device drivers and to be used with add_device(). However, > this is dma-buf so there is no device and no add_device() call to hook. > Unless there are other magic macros to use in this case, I think we're > stuck doing it manually. Have a list of attribute groups and add it to the kobject when you create it so they all get created at the same time. Don't do piece-meal "add one, and then another, and then another" as that just gets messy and complex and impossible to unwind the error conditions from. sysfs_create_groups() is what you need to use here. I need to drop sysfs_create_group() one day... thanks, greg k-h
diff --git a/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps b/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps new file mode 100644 index 000000000000..f83af422fd18 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-dmabuf-caps @@ -0,0 +1,13 @@ +What: /sys/kernel/dmabuf/caps +Date: May 2022 +KernelVersion: v5.20 +Contact: Simon Ser <contact@emersion.fr> +Description: This directory advertises DMA-BUF capabilities supported by the + kernel. + +What: /sys/kernel/dmabuf/caps/sync_file_import_export +Date: May 2022 +KernelVersion: v5.20 +Contact: Simon Ser <contact@emersion.fr> +Description: This file is read-only and advertises support for importing and + exporting sync_files from/to DMA-BUFs. diff --git a/MAINTAINERS b/MAINTAINERS index 11da16bfa123..8966686f7231 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5871,6 +5871,7 @@ L: dri-devel@lists.freedesktop.org L: linaro-mm-sig@lists.linaro.org (moderated for non-subscribers) S: Maintained T: git git://anongit.freedesktop.org/drm/drm-misc +F: Documentation/ABI/testing/sysfs-kernel-dmabuf-caps F: Documentation/driver-api/dma-buf.rst F: drivers/dma-buf/ F: include/linux/*fence.h diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile index 4c9eb53ba3f8..afc874272710 100644 --- a/drivers/dma-buf/Makefile +++ b/drivers/dma-buf/Makefile @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only obj-y := dma-buf.o dma-fence.o dma-fence-array.o dma-fence-chain.o \ - dma-resv.o + dma-resv.o dma-buf-sysfs-caps.o obj-$(CONFIG_DMABUF_HEAPS) += dma-heap.o obj-$(CONFIG_DMABUF_HEAPS) += heaps/ obj-$(CONFIG_SYNC_FILE) += sync_file.o diff --git a/drivers/dma-buf/dma-buf-sysfs-caps.c b/drivers/dma-buf/dma-buf-sysfs-caps.c new file mode 100644 index 000000000000..82b91eb874a9 --- /dev/null +++ b/drivers/dma-buf/dma-buf-sysfs-caps.c @@ -0,0 +1,51 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * DMA-BUF sysfs capabilities. + * + * Copyright (C) 2022 Simon Ser + */ + +#include <linux/kobject.h> +#include <linux/sysfs.h> + +#include "dma-buf-sysfs-caps.h" + +static ssize_t sync_file_import_export_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sysfs_emit(buf, "1\n"); +} + +static struct kobj_attribute dma_buf_sync_file_import_export_attr = + __ATTR_RO(sync_file_import_export); + +static struct attribute *dma_buf_caps_attrs[] = { + &dma_buf_sync_file_import_export_attr.attr, + NULL, +}; + +static const struct attribute_group dma_buf_caps_attr_group = { + .attrs = dma_buf_caps_attrs, +}; + +static struct kobject *dma_buf_caps_kobj; + +int dma_buf_init_sysfs_capabilities(struct kset *kset) +{ + int ret; + + dma_buf_caps_kobj = kobject_create_and_add("caps", &kset->kobj); + if (!dma_buf_caps_kobj) + return -ENOMEM; + + ret = sysfs_create_group(dma_buf_caps_kobj, &dma_buf_caps_attr_group); + if (ret) + kobject_put(dma_buf_caps_kobj); + return ret; +} + +void dma_buf_uninit_sysfs_capabilities(void) +{ + kobject_put(dma_buf_caps_kobj); +} diff --git a/drivers/dma-buf/dma-buf-sysfs-caps.h b/drivers/dma-buf/dma-buf-sysfs-caps.h new file mode 100644 index 000000000000..d7bcef490b31 --- /dev/null +++ b/drivers/dma-buf/dma-buf-sysfs-caps.h @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * DMA-BUF sysfs capabilities. + * + * Copyright (C) 2022 Simon Ser + */ + +#ifndef _DMA_BUF_SYSFS_CAPS_H +#define _DMA_BUF_SYSFS_CAPS_H + +struct kset; + +int dma_buf_init_sysfs_capabilities(struct kset *kset); +void dma_buf_uninit_sysfs_capabilities(void); + +#endif // _DMA_BUF_SYSFS_CAPS_H diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c b/drivers/dma-buf/dma-buf-sysfs-stats.c index 2bba0babcb62..e2e62f83ce18 100644 --- a/drivers/dma-buf/dma-buf-sysfs-stats.c +++ b/drivers/dma-buf/dma-buf-sysfs-stats.c @@ -141,23 +141,14 @@ static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = { .filter = dmabuf_sysfs_uevent_filter, }; -static struct kset *dma_buf_stats_kset; static struct kset *dma_buf_per_buffer_stats_kset; -int dma_buf_init_sysfs_statistics(void) +int dma_buf_init_sysfs_statistics(struct kset *kset) { - dma_buf_stats_kset = kset_create_and_add("dmabuf", - &dmabuf_sysfs_no_uevent_ops, - kernel_kobj); - if (!dma_buf_stats_kset) - return -ENOMEM; - dma_buf_per_buffer_stats_kset = kset_create_and_add("buffers", &dmabuf_sysfs_no_uevent_ops, - &dma_buf_stats_kset->kobj); - if (!dma_buf_per_buffer_stats_kset) { - kset_unregister(dma_buf_stats_kset); + &kset->kobj); + if (!dma_buf_per_buffer_stats_kset) return -ENOMEM; - } return 0; } @@ -165,7 +156,6 @@ int dma_buf_init_sysfs_statistics(void) void dma_buf_uninit_sysfs_statistics(void) { kset_unregister(dma_buf_per_buffer_stats_kset); - kset_unregister(dma_buf_stats_kset); } int dma_buf_stats_setup(struct dma_buf *dmabuf) diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.h b/drivers/dma-buf/dma-buf-sysfs-stats.h index a49c6e2650cc..798c54fb8ee3 100644 --- a/drivers/dma-buf/dma-buf-sysfs-stats.h +++ b/drivers/dma-buf/dma-buf-sysfs-stats.h @@ -8,9 +8,11 @@ #ifndef _DMA_BUF_SYSFS_STATS_H #define _DMA_BUF_SYSFS_STATS_H +struct kset; + #ifdef CONFIG_DMABUF_SYSFS_STATS -int dma_buf_init_sysfs_statistics(void); +int dma_buf_init_sysfs_statistics(struct kset *kset); void dma_buf_uninit_sysfs_statistics(void); int dma_buf_stats_setup(struct dma_buf *dmabuf); @@ -18,7 +20,7 @@ int dma_buf_stats_setup(struct dma_buf *dmabuf); void dma_buf_stats_teardown(struct dma_buf *dmabuf); #else -static inline int dma_buf_init_sysfs_statistics(void) +static inline int dma_buf_init_sysfs_statistics(struct kset *kset) { return 0; } diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 5e1b0534b3ce..b5c5a5050508 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -30,6 +30,7 @@ #include <uapi/linux/dma-buf.h> #include <uapi/linux/magic.h> +#include "dma-buf-sysfs-caps.h" #include "dma-buf-sysfs-stats.h" static inline int is_dma_buf_file(struct file *); @@ -1546,22 +1547,54 @@ static inline void dma_buf_uninit_debugfs(void) } #endif +/* Capabilities and statistics files do not need to send uevents. */ +static int dmabuf_sysfs_uevent_filter(struct kobject *kobj) +{ + return 0; +} + +static const struct kset_uevent_ops dmabuf_sysfs_no_uevent_ops = { + .filter = dmabuf_sysfs_uevent_filter, +}; + +static struct kset *dma_buf_kset; + static int __init dma_buf_init(void) { int ret; - ret = dma_buf_init_sysfs_statistics(); + dma_buf_kset = kset_create_and_add("dmabuf", + &dmabuf_sysfs_no_uevent_ops, + kernel_kobj); + if (!dma_buf_kset) + return -ENOMEM; + + ret = dma_buf_init_sysfs_capabilities(dma_buf_kset); if (ret) - return ret; + goto err_kset; + + ret = dma_buf_init_sysfs_statistics(dma_buf_kset); + if (ret) + goto err_sysfs_caps; dma_buf_mnt = kern_mount(&dma_buf_fs_type); - if (IS_ERR(dma_buf_mnt)) - return PTR_ERR(dma_buf_mnt); + if (IS_ERR(dma_buf_mnt)) { + ret = PTR_ERR(dma_buf_mnt); + goto err_sysfs_stats; + } mutex_init(&db_list.lock); INIT_LIST_HEAD(&db_list.head); dma_buf_init_debugfs(); return 0; + +err_sysfs_stats: + dma_buf_uninit_sysfs_statistics(); +err_sysfs_caps: + dma_buf_uninit_sysfs_capabilities(); +err_kset: + kset_unregister(dma_buf_kset); + return ret; } subsys_initcall(dma_buf_init); @@ -1570,5 +1603,7 @@ static void __exit dma_buf_deinit(void) dma_buf_uninit_debugfs(); kern_unmount(dma_buf_mnt); dma_buf_uninit_sysfs_statistics(); + dma_buf_uninit_sysfs_capabilities(); + kset_unregister(dma_buf_kset); } __exitcall(dma_buf_deinit); diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h index 70e213a0d7d9..ab3afd5da75a 100644 --- a/include/uapi/linux/dma-buf.h +++ b/include/uapi/linux/dma-buf.h @@ -114,6 +114,9 @@ struct dma_buf_sync { * ordering via these fences, it is the respnosibility of userspace to use * locks or other mechanisms to ensure that no other context adds fences or * submits work between steps 1 and 3 above. + * + * Userspace can check the availability of this API via + * /sys/kernel/dmabuf/caps/sync_file_import_export. */ struct dma_buf_export_sync_file { /** @@ -146,6 +149,9 @@ struct dma_buf_export_sync_file { * synchronized APIs such as Vulkan to inter-op with dma-buf consumers * which expect implicit synchronization such as OpenGL or most media * drivers/video. + * + * Userspace can check the availability of this API via + * /sys/kernel/dmabuf/caps/sync_file_import_export. */ struct dma_buf_import_sync_file { /**