| Message ID | 1385416039-3170-1-git-send-email-swarren@wwwdotorg.org (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Mon, Nov 25, 2013 at 1:47 PM, Stephen Warren <swarren@wwwdotorg.org> wrote: > From: Stephen Warren <swarren@nvidia.com> > > dma_request_slave_channel() simply returns NULL whenever DMA channel > lookup fails. Lookup could fail for two distinct reasons: > > a) No DMA specification exists for the channel name. > This includes situations where no DMA specifications exist at all, or > other general lookup problems. > > b) A DMA specification does exist, yet the driver for that channel is not > yet registered. > > Case (b) should trigger deferred probe in client drivers. However, since > they have no way to differentiate the two situations, it cannot. > > Implement new function dma_request_slave_channel_or_err(), which performs Oops, one more s/_or_err/_reason/ Other than that: Acked-by: Dan Williams <dan.j.williams@intel.com> -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 2013-11-25 at 14:47 -0700, Stephen Warren wrote: > From: Stephen Warren <swarren@nvidia.com> > > dma_request_slave_channel() simply returns NULL whenever DMA channel > lookup fails. Lookup could fail for two distinct reasons: > > a) No DMA specification exists for the channel name. > This includes situations where no DMA specifications exist at all, or > other general lookup problems. > > b) A DMA specification does exist, yet the driver for that channel is not > yet registered. > > Case (b) should trigger deferred probe in client drivers. However, since > they have no way to differentiate the two situations, it cannot. > > Implement new function dma_request_slave_channel_or_err(), which performs > identically to dma_request_slave_channel(), except that it returns an > error-pointer rather than NULL, which allows callers to detect when > deferred probe should occur. > > Eventually, all drivers should be converted to this new API, the old API > removed, and the new API renamed to the more desirable name. This patch > doesn't convert the existing API and all drivers in one go, since some > drivers call dma_request_slave_channel() then dma_request_channel() if > that fails. That would require either modifying dma_request_channel() in > the same way, or adding extra error-handling code to all affected > drivers, and there are close to 100 drivers using the other API, rather > than just the 15-20 or so that use dma_request_slave_channel(), which > might be tenable in a single patch. > > acpi_dma_request_slave_chan_by_name() doesn't currently implement > deferred probe. It should, but this will be addressed later. Couple of comments below. [] > --- a/drivers/dma/of-dma.c > +++ b/drivers/dma/of-dma.c [] > @@ -152,17 +152,18 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, > struct of_dma *ofdma; > struct dma_chan *chan; > int count, i; > + int ret_no_channel = -ENODEV; Could we re-use chan for the error as well? > if (!np || !name) { > pr_err("%s: not enough information provided\n", __func__); > - return NULL; > + return ERR_PTR(-ENODEV); > } > > count = of_property_count_strings(np, "dma-names"); > if (count < 0) { > pr_err("%s: dma-names property of node '%s' missing or empty\n", > __func__, np->full_name); > - return NULL; > + return ERR_PTR(-ENODEV); > } > > for (i = 0; i < count; i++) { > @@ -174,8 +175,10 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, > > if (ofdma) if (ofdma) { ... > chan = ofdma->of_dma_xlate(&dma_spec, ofdma); > - else > + else { } else { to keep style. > + ret_no_channel = -EPROBE_DEFER; > chan = NULL; > + } > > mutex_unlock(&of_dma_lock); > > @@ -185,7 +188,7 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, > return chan; > } > > - return NULL; > + return ERR_PTR(ret_no_channel); > } -- Andy Shevchenko <andriy.shevchenko@intel.com> Intel Finland Oy --------------------------------------------------------------------- Intel Finland Oy Registered Address: PL 281, 00181 Helsinki Business Identity Code: 0357606 - 4 Domiciled in Helsinki This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.
On 11/26/2013 06:59 AM, Shevchenko, Andriy wrote: > On Mon, 2013-11-25 at 14:47 -0700, Stephen Warren wrote: >> From: Stephen Warren <swarren@nvidia.com> >> >> dma_request_slave_channel() simply returns NULL whenever DMA channel >> lookup fails. Lookup could fail for two distinct reasons: >> >> a) No DMA specification exists for the channel name. >> This includes situations where no DMA specifications exist at all, or >> other general lookup problems. >> >> b) A DMA specification does exist, yet the driver for that channel is not >> yet registered. >> >> Case (b) should trigger deferred probe in client drivers. However, since >> they have no way to differentiate the two situations, it cannot. >> >> Implement new function dma_request_slave_channel_or_err(), which performs >> identically to dma_request_slave_channel(), except that it returns an >> error-pointer rather than NULL, which allows callers to detect when >> deferred probe should occur. >> >> Eventually, all drivers should be converted to this new API, the old API >> removed, and the new API renamed to the more desirable name. This patch >> doesn't convert the existing API and all drivers in one go, since some >> drivers call dma_request_slave_channel() then dma_request_channel() if >> that fails. That would require either modifying dma_request_channel() in >> the same way, or adding extra error-handling code to all affected >> drivers, and there are close to 100 drivers using the other API, rather >> than just the 15-20 or so that use dma_request_slave_channel(), which >> might be tenable in a single patch. >> >> acpi_dma_request_slave_chan_by_name() doesn't currently implement >> deferred probe. It should, but this will be addressed later. > > Couple of comments below. > > [] > >> --- a/drivers/dma/of-dma.c >> +++ b/drivers/dma/of-dma.c > > [] > >> @@ -152,17 +152,18 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, >> struct of_dma *ofdma; >> struct dma_chan *chan; >> int count, i; >> + int ret_no_channel = -ENODEV; > > Could we re-use chan for the error as well? No, because that gets over-written each time ofdma->of_dma_xlate() is called, and that could fail and cause the result not to be returned, and then we would have lost any -EPROBE_DEFERRED value that was stored there to be returned in the nothing-found case. >> @@ -174,8 +175,10 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, >> >> if (ofdma) > > if (ofdma) { > ... > >> chan = ofdma->of_dma_xlate(&dma_spec, ofdma); >> - else >> + else { > > } else { > > to keep style. OK, I've fixed that up locally. I assume it's not worth a repost just for that change, although I will repost if the DMA maintainers want to create the topic branches rather than me, but there's been no word on that yet. -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Nov 26, 2013 at 8:37 AM, Stephen Warren <swarren@wwwdotorg.org> wrote: > On 11/26/2013 06:59 AM, Shevchenko, Andriy wrote: >> On Mon, 2013-11-25 at 14:47 -0700, Stephen Warren wrote: >>> From: Stephen Warren <swarren@nvidia.com> >>> >>> dma_request_slave_channel() simply returns NULL whenever DMA channel >>> lookup fails. Lookup could fail for two distinct reasons: >>> >>> a) No DMA specification exists for the channel name. >>> This includes situations where no DMA specifications exist at all, or >>> other general lookup problems. >>> >>> b) A DMA specification does exist, yet the driver for that channel is not >>> yet registered. >>> >>> Case (b) should trigger deferred probe in client drivers. However, since >>> they have no way to differentiate the two situations, it cannot. >>> >>> Implement new function dma_request_slave_channel_or_err(), which performs >>> identically to dma_request_slave_channel(), except that it returns an >>> error-pointer rather than NULL, which allows callers to detect when >>> deferred probe should occur. >>> >>> Eventually, all drivers should be converted to this new API, the old API >>> removed, and the new API renamed to the more desirable name. This patch >>> doesn't convert the existing API and all drivers in one go, since some >>> drivers call dma_request_slave_channel() then dma_request_channel() if >>> that fails. That would require either modifying dma_request_channel() in >>> the same way, or adding extra error-handling code to all affected >>> drivers, and there are close to 100 drivers using the other API, rather >>> than just the 15-20 or so that use dma_request_slave_channel(), which >>> might be tenable in a single patch. >>> >>> acpi_dma_request_slave_chan_by_name() doesn't currently implement >>> deferred probe. It should, but this will be addressed later. >> >> Couple of comments below. >> >> [] >> >>> --- a/drivers/dma/of-dma.c >>> +++ b/drivers/dma/of-dma.c >> >> [] >> >>> @@ -152,17 +152,18 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, >>> struct of_dma *ofdma; >>> struct dma_chan *chan; >>> int count, i; >>> + int ret_no_channel = -ENODEV; >> >> Could we re-use chan for the error as well? > > No, because that gets over-written each time ofdma->of_dma_xlate() is > called, and that could fail and cause the result not to be returned, and > then we would have lost any -EPROBE_DEFERRED value that was stored there > to be returned in the nothing-found case. > >>> @@ -174,8 +175,10 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, >>> >>> if (ofdma) >> >> if (ofdma) { >> ... >> >>> chan = ofdma->of_dma_xlate(&dma_spec, ofdma); >>> - else >>> + else { >> >> } else { >> >> to keep style. > > OK, I've fixed that up locally. I assume it's not worth a repost just > for that change, although I will repost if the DMA maintainers want to > create the topic branches rather than me, but there's been no word on > that yet. That might be best and Vinod should be back. Vinod do you want to queue this one up to a topic branch so that the arm-soc tree can pull it? -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 11/26/2013 09:44 AM, Dan Williams wrote: > On Tue, Nov 26, 2013 at 8:37 AM, Stephen Warren <swarren@wwwdotorg.org> wrote: >> On 11/26/2013 06:59 AM, Shevchenko, Andriy wrote: >>> On Mon, 2013-11-25 at 14:47 -0700, Stephen Warren wrote: >>>> From: Stephen Warren <swarren@nvidia.com> >>>> >>>> dma_request_slave_channel() simply returns NULL whenever DMA channel >>>> lookup fails. Lookup could fail for two distinct reasons: >>>> >>>> a) No DMA specification exists for the channel name. >>>> This includes situations where no DMA specifications exist at all, or >>>> other general lookup problems. >>>> >>>> b) A DMA specification does exist, yet the driver for that channel is not >>>> yet registered. >>>> >>>> Case (b) should trigger deferred probe in client drivers. However, since >>>> they have no way to differentiate the two situations, it cannot. >>>> >>>> Implement new function dma_request_slave_channel_or_err(), which performs >>>> identically to dma_request_slave_channel(), except that it returns an >>>> error-pointer rather than NULL, which allows callers to detect when >>>> deferred probe should occur. >>>> >>>> Eventually, all drivers should be converted to this new API, the old API >>>> removed, and the new API renamed to the more desirable name. This patch >>>> doesn't convert the existing API and all drivers in one go, since some >>>> drivers call dma_request_slave_channel() then dma_request_channel() if >>>> that fails. That would require either modifying dma_request_channel() in >>>> the same way, or adding extra error-handling code to all affected >>>> drivers, and there are close to 100 drivers using the other API, rather >>>> than just the 15-20 or so that use dma_request_slave_channel(), which >>>> might be tenable in a single patch. >>>> >>>> acpi_dma_request_slave_chan_by_name() doesn't currently implement >>>> deferred probe. It should, but this will be addressed later. ... >> OK, I've fixed that up locally. I assume it's not worth a repost just >> for that change, although I will repost if the DMA maintainers want to >> create the topic branches rather than me, but there's been no word on >> that yet. > > That might be best and Vinod should be back. Vinod do you want to > queue this one up to a topic branch so that the arm-soc tree can pull > it? Vinod, V4 of this patch addressed Dan's final minor comments on this patch. Does it look OK to you? If you could apply it to a topic branch[1] soon, that would be extremely helpful; I'm waiting for this patch (and also "dma: add dma_get_any_slave_channel(), for use in of_xlate()") in order to apply a lot of others. [1] see notes I posted in the patch: This patch is a dependency for: * A series that reworks many of the Tegra drivers. * A series that enhances ASoC's dmaengine code to support deferred probe. As such, it needs to go into a topic branch on its own, based directly on 3.13-rc1. If the DMA maintainers ack the patches I'm happy to create this topic branch myself and send a pull request to the DMA tree. Or the patches can be applied to a topic branch by the DMA maintainers and I will merge their topic branch into the Tegra rework branch that I mentioned. Thanks. -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index ea806bdc12ef..e17e9b22d85e 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -540,6 +540,8 @@ EXPORT_SYMBOL_GPL(dma_get_slave_channel); * @mask: capabilities that the channel must satisfy * @fn: optional callback to disposition available channels * @fn_param: opaque parameter to pass to dma_filter_fn + * + * Returns pointer to appropriate DMA channel on success or NULL. */ struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param) @@ -591,18 +593,43 @@ EXPORT_SYMBOL_GPL(__dma_request_channel); * dma_request_slave_channel - try to allocate an exclusive slave channel * @dev: pointer to client device structure * @name: slave channel name + * + * Returns pointer to appropriate DMA channel on success or an error pointer. */ -struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name) +struct dma_chan *dma_request_slave_channel_reason(struct device *dev, + const char *name) { + struct dma_chan *chan; + /* If device-tree is present get slave info from here */ if (dev->of_node) return of_dma_request_slave_channel(dev->of_node, name); /* If device was enumerated by ACPI get slave info from here */ - if (ACPI_HANDLE(dev)) - return acpi_dma_request_slave_chan_by_name(dev, name); + if (ACPI_HANDLE(dev)) { + chan = acpi_dma_request_slave_chan_by_name(dev, name); + if (chan) + return chan; + } - return NULL; + return ERR_PTR(-ENODEV); +} +EXPORT_SYMBOL_GPL(dma_request_slave_channel_reason); + +/** + * dma_request_slave_channel - try to allocate an exclusive slave channel + * @dev: pointer to client device structure + * @name: slave channel name + * + * Returns pointer to appropriate DMA channel on success or NULL. + */ +struct dma_chan *dma_request_slave_channel(struct device *dev, + const char *name) +{ + struct dma_chan *ch = dma_request_slave_channel_reason(dev, name); + if (IS_ERR(ch)) + return NULL; + return ch; } EXPORT_SYMBOL_GPL(dma_request_slave_channel); diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c index 0b88dd3d05f4..f68e25c9af3a 100644 --- a/drivers/dma/of-dma.c +++ b/drivers/dma/of-dma.c @@ -143,7 +143,7 @@ static int of_dma_match_channel(struct device_node *np, const char *name, * @np: device node to get DMA request from * @name: name of desired channel * - * Returns pointer to appropriate dma channel on success or NULL on error. + * Returns pointer to appropriate DMA channel on success or an error pointer. */ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, const char *name) @@ -152,17 +152,18 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, struct of_dma *ofdma; struct dma_chan *chan; int count, i; + int ret_no_channel = -ENODEV; if (!np || !name) { pr_err("%s: not enough information provided\n", __func__); - return NULL; + return ERR_PTR(-ENODEV); } count = of_property_count_strings(np, "dma-names"); if (count < 0) { pr_err("%s: dma-names property of node '%s' missing or empty\n", __func__, np->full_name); - return NULL; + return ERR_PTR(-ENODEV); } for (i = 0; i < count; i++) { @@ -174,8 +175,10 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, if (ofdma) chan = ofdma->of_dma_xlate(&dma_spec, ofdma); - else + else { + ret_no_channel = -EPROBE_DEFER; chan = NULL; + } mutex_unlock(&of_dma_lock); @@ -185,7 +188,7 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np, return chan; } - return NULL; + return ERR_PTR(ret_no_channel); } /** diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index 41cf0c399288..ed92b30a02fd 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -22,6 +22,7 @@ #define LINUX_DMAENGINE_H #include <linux/device.h> +#include <linux/err.h> #include <linux/uio.h> #include <linux/bug.h> #include <linux/scatterlist.h> @@ -1040,6 +1041,8 @@ enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx); void dma_issue_pending_all(void); struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param); +struct dma_chan *dma_request_slave_channel_reason(struct device *dev, + const char *name); struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name); void dma_release_channel(struct dma_chan *chan); #else @@ -1063,6 +1066,11 @@ static inline struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask, { return NULL; } +static inline struct dma_chan *dma_request_slave_channel_reason( + struct device *dev, const char *name) +{ + return ERR_PTR(-ENODEV); +} static inline struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name) {