| Message ID | 1538400237-28766-1-git-send-email-fabrice.gasnier@st.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | pwm: sysfs: fix exporting PWM channel | expand |
On 1.10.2018 15:23, Fabrice Gasnier wrote: > Since commit 7e5d1fd75c3d ("pwm: Set class for exported channels in sysfs") > - it's not possible to export more than one PWM channel > - ABI has changed, as a side effect. It may cause bad behavior as pwmchip > attributes are wrongly added to pwm channels and report wrong values. > See [1] and [2]. > > One purpose of the original patch is to send uevents to udev, when exporting a > PWM channel through the sysfs. This series: > - Reverts the original patch. > - Proposes a new way to send notifications to be used by udev rules. > > - With this series: > $ echo 0 > /sys/class/pwm/pwmchip0/export > $ ls /sys/class/pwm > pwmchip0 pwmchip4 > > $ ls /sys/class/pwm/pwmchip0/pwm0/ > capture enable polarity uevent > duty_cycle period power > > - Without this series: > $ echo 0 > /sys/class/pwm/pwmchip0/export > $ ls /sys/class/pwm > pwm0 pwmchip0 pwmchip4 > > $ ls /sys/class/pwm/pwmchip0/pwm0/ > capture duty_cycle export period power uevent > device enable npwm polarity subsystem unexport > > - Backtrace when exporting a 2nd channel (0) on a separate pwmchip device: > $ echo 0 > /sys/class/pwm/pwmchip4/export > [ 95.286558] sysfs: cannot create duplicate filename '/class/pwm/pwm0' > [ 95.293630] CPU: 0 PID: 54 Comm: sh Not tainted 4.19.0-rc6-00013-g00b49b0 #151 > [ 95.301344] Hardware name: STM32 (Device Tree Support) > [ 95.306833] [<0000c155>] (unwind_backtrace) from [<0000b273>] (show_stack+0xb/0xc) > [ 95.315136] [<0000b273>] (show_stack) from [<00092455>] (sysfs_warn_dup+0x31/0x48) > [ 95.323247] [<00092455>] (sysfs_warn_dup) from [<00092635>] (sysfs_do_create_link_sd+0x75/0x88) > [ 95.332539] [<00092635>] (sysfs_do_create_link_sd) from [<00125823>] (device_add+0x133/0x3b0) > [ 95.341694] [<00125823>] (device_add) from [<001059ed>] (export_store+0xb5/0x12c) > [ 95.349761] [<001059ed>] (export_store) from [<00091911>] (kernfs_fop_write+0x87/0xda) > [ 95.358150] [<00091911>] (kernfs_fop_write) from [<0005beb1>] (__vfs_write+0x1d/0xe0) > [ 95.366295] [<0005beb1>] (__vfs_write) from [<0005bfe7>] (vfs_write+0x4f/0x7c) > [ 95.374053] [<0005bfe7>] (vfs_write) from [<0005c0bf>] (ksys_write+0x33/0x70) > [ 95.381708] [<0005c0bf>] (ksys_write) from [<00009001>] (ret_fast_syscall+0x1/0x58) > [ 95.389682] Exception stack(0x01bcffa8 to 0x01bcfff0) > [ 95.394946] ffa0: 00000000 00c4883c 00000001 00c4e590 00000002 00000004 > [ 95.403639] ffc0: 00000000 00c4883c 00c4cbe8 00000004 00000002 00000020 00000000 00c4d008 > [ 95.412223] ffe0: 00c29151 00c4cbe8 00c17833 00c13c0c > -sh: write error: File exists > > [1] https://lkml.org/lkml/2018/9/25/713 > [2] https://lkml.org/lkml/2018/9/25/447 The [2] report came from me. I tested both patches on my i.MX6 boards and it works just fine. Thanks for the fix Fabrice! Michal > > --- > Changes in v2: > - update revert commit message > - new patch 2/2 to propose uevent notification (change) on pwmchip > > Fabrice Gasnier (2): > Revert "pwm: Set class for exported channels in sysfs" > pwm: send a uevent on the pwmchip device upon channel sysfs (un)export > > drivers/pwm/sysfs.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) >
On Mon, Oct 01, 2018 at 03:23:55PM +0200, Fabrice Gasnier wrote: > Since commit 7e5d1fd75c3d ("pwm: Set class for exported channels in sysfs") > - it's not possible to export more than one PWM channel > - ABI has changed, as a side effect. It may cause bad behavior as pwmchip > attributes are wrongly added to pwm channels and report wrong values. > See [1] and [2]. > > One purpose of the original patch is to send uevents to udev, when exporting a > PWM channel through the sysfs. This series: > - Reverts the original patch. > - Proposes a new way to send notifications to be used by udev rules. > > - With this series: > $ echo 0 > /sys/class/pwm/pwmchip0/export > $ ls /sys/class/pwm > pwmchip0 pwmchip4 > > $ ls /sys/class/pwm/pwmchip0/pwm0/ > capture enable polarity uevent > duty_cycle period power > > - Without this series: > $ echo 0 > /sys/class/pwm/pwmchip0/export > $ ls /sys/class/pwm > pwm0 pwmchip0 pwmchip4 > > $ ls /sys/class/pwm/pwmchip0/pwm0/ > capture duty_cycle export period power uevent > device enable npwm polarity subsystem unexport > > - Backtrace when exporting a 2nd channel (0) on a separate pwmchip device: > $ echo 0 > /sys/class/pwm/pwmchip4/export > [ 95.286558] sysfs: cannot create duplicate filename '/class/pwm/pwm0' > [ 95.293630] CPU: 0 PID: 54 Comm: sh Not tainted 4.19.0-rc6-00013-g00b49b0 #151 > [ 95.301344] Hardware name: STM32 (Device Tree Support) > [ 95.306833] [<0000c155>] (unwind_backtrace) from [<0000b273>] (show_stack+0xb/0xc) > [ 95.315136] [<0000b273>] (show_stack) from [<00092455>] (sysfs_warn_dup+0x31/0x48) > [ 95.323247] [<00092455>] (sysfs_warn_dup) from [<00092635>] (sysfs_do_create_link_sd+0x75/0x88) > [ 95.332539] [<00092635>] (sysfs_do_create_link_sd) from [<00125823>] (device_add+0x133/0x3b0) > [ 95.341694] [<00125823>] (device_add) from [<001059ed>] (export_store+0xb5/0x12c) > [ 95.349761] [<001059ed>] (export_store) from [<00091911>] (kernfs_fop_write+0x87/0xda) > [ 95.358150] [<00091911>] (kernfs_fop_write) from [<0005beb1>] (__vfs_write+0x1d/0xe0) > [ 95.366295] [<0005beb1>] (__vfs_write) from [<0005bfe7>] (vfs_write+0x4f/0x7c) > [ 95.374053] [<0005bfe7>] (vfs_write) from [<0005c0bf>] (ksys_write+0x33/0x70) > [ 95.381708] [<0005c0bf>] (ksys_write) from [<00009001>] (ret_fast_syscall+0x1/0x58) > [ 95.389682] Exception stack(0x01bcffa8 to 0x01bcfff0) > [ 95.394946] ffa0: 00000000 00c4883c 00000001 00c4e590 00000002 00000004 > [ 95.403639] ffc0: 00000000 00c4883c 00c4cbe8 00000004 00000002 00000020 00000000 00c4d008 > [ 95.412223] ffe0: 00c29151 00c4cbe8 00c17833 00c13c0c > -sh: write error: File exists > > [1] https://lkml.org/lkml/2018/9/25/713 > [2] https://lkml.org/lkml/2018/9/25/447 > > --- > Changes in v2: > - update revert commit message > - new patch 2/2 to propose uevent notification (change) on pwmchip > > Fabrice Gasnier (2): > Revert "pwm: Set class for exported channels in sysfs" > pwm: send a uevent on the pwmchip device upon channel sysfs (un)export > > drivers/pwm/sysfs.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) Both patches applied, thanks. What do you think would be the importance of getting this into stable kernels? We can't get one of the patches in without the other, so they'd both have to be backported. The second one is still fairly small, so would qualify for stable, I think. However, given that it's taken a long time for somebody to notice this, I'm not sure if this is something that people care about too much in the stable kernels. Thierry
Am 12.10.2018 um 13:55 schrieb Thierry Reding: > On Mon, Oct 01, 2018 at 03:23:55PM +0200, Fabrice Gasnier wrote: >> Since commit 7e5d1fd75c3d ("pwm: Set class for exported channels in sysfs") >> - it's not possible to export more than one PWM channel >> - ABI has changed, as a side effect. It may cause bad behavior as pwmchip >> attributes are wrongly added to pwm channels and report wrong values. >> See [1] and [2]. >> >> One purpose of the original patch is to send uevents to udev, when exporting a >> PWM channel through the sysfs. This series: >> - Reverts the original patch. >> - Proposes a new way to send notifications to be used by udev rules. >> >> - With this series: >> $ echo 0 > /sys/class/pwm/pwmchip0/export >> $ ls /sys/class/pwm >> pwmchip0 pwmchip4 >> >> $ ls /sys/class/pwm/pwmchip0/pwm0/ >> capture enable polarity uevent >> duty_cycle period power >> >> - Without this series: >> $ echo 0 > /sys/class/pwm/pwmchip0/export >> $ ls /sys/class/pwm >> pwm0 pwmchip0 pwmchip4 >> >> $ ls /sys/class/pwm/pwmchip0/pwm0/ >> capture duty_cycle export period power uevent >> device enable npwm polarity subsystem unexport >> >> - Backtrace when exporting a 2nd channel (0) on a separate pwmchip device: >> $ echo 0 > /sys/class/pwm/pwmchip4/export >> [ 95.286558] sysfs: cannot create duplicate filename '/class/pwm/pwm0' >> [ 95.293630] CPU: 0 PID: 54 Comm: sh Not tainted 4.19.0-rc6-00013-g00b49b0 #151 >> [ 95.301344] Hardware name: STM32 (Device Tree Support) >> [ 95.306833] [<0000c155>] (unwind_backtrace) from [<0000b273>] (show_stack+0xb/0xc) >> [ 95.315136] [<0000b273>] (show_stack) from [<00092455>] (sysfs_warn_dup+0x31/0x48) >> [ 95.323247] [<00092455>] (sysfs_warn_dup) from [<00092635>] (sysfs_do_create_link_sd+0x75/0x88) >> [ 95.332539] [<00092635>] (sysfs_do_create_link_sd) from [<00125823>] (device_add+0x133/0x3b0) >> [ 95.341694] [<00125823>] (device_add) from [<001059ed>] (export_store+0xb5/0x12c) >> [ 95.349761] [<001059ed>] (export_store) from [<00091911>] (kernfs_fop_write+0x87/0xda) >> [ 95.358150] [<00091911>] (kernfs_fop_write) from [<0005beb1>] (__vfs_write+0x1d/0xe0) >> [ 95.366295] [<0005beb1>] (__vfs_write) from [<0005bfe7>] (vfs_write+0x4f/0x7c) >> [ 95.374053] [<0005bfe7>] (vfs_write) from [<0005c0bf>] (ksys_write+0x33/0x70) >> [ 95.381708] [<0005c0bf>] (ksys_write) from [<00009001>] (ret_fast_syscall+0x1/0x58) >> [ 95.389682] Exception stack(0x01bcffa8 to 0x01bcfff0) >> [ 95.394946] ffa0: 00000000 00c4883c 00000001 00c4e590 00000002 00000004 >> [ 95.403639] ffc0: 00000000 00c4883c 00c4cbe8 00000004 00000002 00000020 00000000 00c4d008 >> [ 95.412223] ffe0: 00c29151 00c4cbe8 00c17833 00c13c0c >> -sh: write error: File exists >> >> [1] https://lkml.org/lkml/2018/9/25/713 >> [2] https://lkml.org/lkml/2018/9/25/447 >> >> --- >> Changes in v2: >> - update revert commit message >> - new patch 2/2 to propose uevent notification (change) on pwmchip >> >> Fabrice Gasnier (2): >> Revert "pwm: Set class for exported channels in sysfs" >> pwm: send a uevent on the pwmchip device upon channel sysfs (un)export >> >> drivers/pwm/sysfs.c | 12 +++++++++++- >> 1 file changed, 11 insertions(+), 1 deletion(-) > Both patches applied, thanks. What do you think would be the importance > of getting this into stable kernels? We can't get one of the patches in > without the other, so they'd both have to be backported. The second one > is still fairly small, so would qualify for stable, I think. I think the revert patch should go to stable, because it fixes a regression. Thanks > > However, given that it's taken a long time for somebody to notice this, > I'm not sure if this is something that people care about too much in the > stable kernels. > > Thierry
On 10/12/2018 02:15 PM, Stefan Wahren wrote: > Am 12.10.2018 um 13:55 schrieb Thierry Reding: >> On Mon, Oct 01, 2018 at 03:23:55PM +0200, Fabrice Gasnier wrote: >>> Since commit 7e5d1fd75c3d ("pwm: Set class for exported channels in sysfs") >>> - it's not possible to export more than one PWM channel >>> - ABI has changed, as a side effect. It may cause bad behavior as pwmchip >>> attributes are wrongly added to pwm channels and report wrong values. >>> See [1] and [2]. >>> >>> One purpose of the original patch is to send uevents to udev, when exporting a >>> PWM channel through the sysfs. This series: >>> - Reverts the original patch. >>> - Proposes a new way to send notifications to be used by udev rules. >>> >>> - With this series: >>> $ echo 0 > /sys/class/pwm/pwmchip0/export >>> $ ls /sys/class/pwm >>> pwmchip0 pwmchip4 >>> >>> $ ls /sys/class/pwm/pwmchip0/pwm0/ >>> capture enable polarity uevent >>> duty_cycle period power >>> >>> - Without this series: >>> $ echo 0 > /sys/class/pwm/pwmchip0/export >>> $ ls /sys/class/pwm >>> pwm0 pwmchip0 pwmchip4 >>> >>> $ ls /sys/class/pwm/pwmchip0/pwm0/ >>> capture duty_cycle export period power uevent >>> device enable npwm polarity subsystem unexport >>> >>> - Backtrace when exporting a 2nd channel (0) on a separate pwmchip device: >>> $ echo 0 > /sys/class/pwm/pwmchip4/export >>> [ 95.286558] sysfs: cannot create duplicate filename '/class/pwm/pwm0' >>> [ 95.293630] CPU: 0 PID: 54 Comm: sh Not tainted 4.19.0-rc6-00013-g00b49b0 #151 >>> [ 95.301344] Hardware name: STM32 (Device Tree Support) >>> [ 95.306833] [<0000c155>] (unwind_backtrace) from [<0000b273>] (show_stack+0xb/0xc) >>> [ 95.315136] [<0000b273>] (show_stack) from [<00092455>] (sysfs_warn_dup+0x31/0x48) >>> [ 95.323247] [<00092455>] (sysfs_warn_dup) from [<00092635>] (sysfs_do_create_link_sd+0x75/0x88) >>> [ 95.332539] [<00092635>] (sysfs_do_create_link_sd) from [<00125823>] (device_add+0x133/0x3b0) >>> [ 95.341694] [<00125823>] (device_add) from [<001059ed>] (export_store+0xb5/0x12c) >>> [ 95.349761] [<001059ed>] (export_store) from [<00091911>] (kernfs_fop_write+0x87/0xda) >>> [ 95.358150] [<00091911>] (kernfs_fop_write) from [<0005beb1>] (__vfs_write+0x1d/0xe0) >>> [ 95.366295] [<0005beb1>] (__vfs_write) from [<0005bfe7>] (vfs_write+0x4f/0x7c) >>> [ 95.374053] [<0005bfe7>] (vfs_write) from [<0005c0bf>] (ksys_write+0x33/0x70) >>> [ 95.381708] [<0005c0bf>] (ksys_write) from [<00009001>] (ret_fast_syscall+0x1/0x58) >>> [ 95.389682] Exception stack(0x01bcffa8 to 0x01bcfff0) >>> [ 95.394946] ffa0: 00000000 00c4883c 00000001 00c4e590 00000002 00000004 >>> [ 95.403639] ffc0: 00000000 00c4883c 00c4cbe8 00000004 00000002 00000020 00000000 00c4d008 >>> [ 95.412223] ffe0: 00c29151 00c4cbe8 00c17833 00c13c0c >>> -sh: write error: File exists >>> >>> [1] https://lkml.org/lkml/2018/9/25/713 >>> [2] https://lkml.org/lkml/2018/9/25/447 >>> >>> --- >>> Changes in v2: >>> - update revert commit message >>> - new patch 2/2 to propose uevent notification (change) on pwmchip >>> >>> Fabrice Gasnier (2): >>> Revert "pwm: Set class for exported channels in sysfs" >>> pwm: send a uevent on the pwmchip device upon channel sysfs (un)export >>> >>> drivers/pwm/sysfs.c | 12 +++++++++++- >>> 1 file changed, 11 insertions(+), 1 deletion(-) >> Both patches applied, thanks. What do you think would be the importance >> of getting this into stable kernels? We can't get one of the patches in >> without the other, so they'd both have to be backported. The second one >> is still fairly small, so would qualify for stable, I think. > I think the revert patch should go to stable, because it fixes a regression. > Hi, Thierry, Thanks for taking these. I also think at least the 1st patch (revert) should be backported in stable branch. Not taking the second one may lead to another issue for the users that now expect uevents. This is replacement patch to the original one. So, I'd advise to push both: revert + replacement patch. Fabrice > Thanks >> >> However, given that it's taken a long time for somebody to notice this, >> I'm not sure if this is something that people care about too much in the >> stable kernels>> >> Thierry
On 12.10.2018 14:36, Fabrice Gasnier wrote: > On 10/12/2018 02:15 PM, Stefan Wahren wrote: >> Am 12.10.2018 um 13:55 schrieb Thierry Reding: >>> On Mon, Oct 01, 2018 at 03:23:55PM +0200, Fabrice Gasnier wrote: >>>> Since commit 7e5d1fd75c3d ("pwm: Set class for exported channels in sysfs") >>>> - it's not possible to export more than one PWM channel >>>> - ABI has changed, as a side effect. It may cause bad behavior as pwmchip >>>> attributes are wrongly added to pwm channels and report wrong values. >>>> See [1] and [2]. >>>> >>>> One purpose of the original patch is to send uevents to udev, when exporting a >>>> PWM channel through the sysfs. This series: >>>> - Reverts the original patch. >>>> - Proposes a new way to send notifications to be used by udev rules. >>>> >>>> - With this series: >>>> $ echo 0 > /sys/class/pwm/pwmchip0/export >>>> $ ls /sys/class/pwm >>>> pwmchip0 pwmchip4 >>>> >>>> $ ls /sys/class/pwm/pwmchip0/pwm0/ >>>> capture enable polarity uevent >>>> duty_cycle period power >>>> >>>> - Without this series: >>>> $ echo 0 > /sys/class/pwm/pwmchip0/export >>>> $ ls /sys/class/pwm >>>> pwm0 pwmchip0 pwmchip4 >>>> >>>> $ ls /sys/class/pwm/pwmchip0/pwm0/ >>>> capture duty_cycle export period power uevent >>>> device enable npwm polarity subsystem unexport >>>> >>>> - Backtrace when exporting a 2nd channel (0) on a separate pwmchip device: >>>> $ echo 0 > /sys/class/pwm/pwmchip4/export >>>> [ 95.286558] sysfs: cannot create duplicate filename '/class/pwm/pwm0' >>>> [ 95.293630] CPU: 0 PID: 54 Comm: sh Not tainted 4.19.0-rc6-00013-g00b49b0 #151 >>>> [ 95.301344] Hardware name: STM32 (Device Tree Support) >>>> [ 95.306833] [<0000c155>] (unwind_backtrace) from [<0000b273>] (show_stack+0xb/0xc) >>>> [ 95.315136] [<0000b273>] (show_stack) from [<00092455>] (sysfs_warn_dup+0x31/0x48) >>>> [ 95.323247] [<00092455>] (sysfs_warn_dup) from [<00092635>] (sysfs_do_create_link_sd+0x75/0x88) >>>> [ 95.332539] [<00092635>] (sysfs_do_create_link_sd) from [<00125823>] (device_add+0x133/0x3b0) >>>> [ 95.341694] [<00125823>] (device_add) from [<001059ed>] (export_store+0xb5/0x12c) >>>> [ 95.349761] [<001059ed>] (export_store) from [<00091911>] (kernfs_fop_write+0x87/0xda) >>>> [ 95.358150] [<00091911>] (kernfs_fop_write) from [<0005beb1>] (__vfs_write+0x1d/0xe0) >>>> [ 95.366295] [<0005beb1>] (__vfs_write) from [<0005bfe7>] (vfs_write+0x4f/0x7c) >>>> [ 95.374053] [<0005bfe7>] (vfs_write) from [<0005c0bf>] (ksys_write+0x33/0x70) >>>> [ 95.381708] [<0005c0bf>] (ksys_write) from [<00009001>] (ret_fast_syscall+0x1/0x58) >>>> [ 95.389682] Exception stack(0x01bcffa8 to 0x01bcfff0) >>>> [ 95.394946] ffa0: 00000000 00c4883c 00000001 00c4e590 00000002 00000004 >>>> [ 95.403639] ffc0: 00000000 00c4883c 00c4cbe8 00000004 00000002 00000020 00000000 00c4d008 >>>> [ 95.412223] ffe0: 00c29151 00c4cbe8 00c17833 00c13c0c >>>> -sh: write error: File exists >>>> >>>> [1] https://lkml.org/lkml/2018/9/25/713 >>>> [2] https://lkml.org/lkml/2018/9/25/447 >>>> >>>> --- >>>> Changes in v2: >>>> - update revert commit message >>>> - new patch 2/2 to propose uevent notification (change) on pwmchip >>>> >>>> Fabrice Gasnier (2): >>>> Revert "pwm: Set class for exported channels in sysfs" >>>> pwm: send a uevent on the pwmchip device upon channel sysfs (un)export >>>> >>>> drivers/pwm/sysfs.c | 12 +++++++++++- >>>> 1 file changed, 11 insertions(+), 1 deletion(-) >>> Both patches applied, thanks. What do you think would be the importance >>> of getting this into stable kernels? We can't get one of the patches in >>> without the other, so they'd both have to be backported. The second one >>> is still fairly small, so would qualify for stable, I think. >> I think the revert patch should go to stable, because it fixes a regression. >> > > Hi, > > Thierry, Thanks for taking these. > I also think at least the 1st patch (revert) should be backported in > stable branch. Not taking the second one may lead to another issue for > the users that now expect uevents. This is replacement patch to the > original one. So, I'd advise to push both: revert + replacement patch. I also vote for pushing both. M. >>> However, given that it's taken a long time for somebody to notice this, >>> I'm not sure if this is something that people care about too much in the >>> stable kernels>> >>> Thierry
Since commit 7e5d1fd75c3d ("pwm: Set class for exported channels in sysfs") - it's not possible to export more than one PWM channel - ABI has changed, as a side effect. It may cause bad behavior as pwmchip attributes are wrongly added to pwm channels and report wrong values. See [1] and [2]. One purpose of the original patch is to send uevents to udev, when exporting a PWM channel through the sysfs. This series: - Reverts the original patch. - Proposes a new way to send notifications to be used by udev rules. - With this series: $ echo 0 > /sys/class/pwm/pwmchip0/export $ ls /sys/class/pwm pwmchip0 pwmchip4 $ ls /sys/class/pwm/pwmchip0/pwm0/ capture enable polarity uevent duty_cycle period power - Without this series: $ echo 0 > /sys/class/pwm/pwmchip0/export $ ls /sys/class/pwm pwm0 pwmchip0 pwmchip4 $ ls /sys/class/pwm/pwmchip0/pwm0/ capture duty_cycle export period power uevent device enable npwm polarity subsystem unexport - Backtrace when exporting a 2nd channel (0) on a separate pwmchip device: $ echo 0 > /sys/class/pwm/pwmchip4/export [ 95.286558] sysfs: cannot create duplicate filename '/class/pwm/pwm0' [ 95.293630] CPU: 0 PID: 54 Comm: sh Not tainted 4.19.0-rc6-00013-g00b49b0 #151 [ 95.301344] Hardware name: STM32 (Device Tree Support) [ 95.306833] [<0000c155>] (unwind_backtrace) from [<0000b273>] (show_stack+0xb/0xc) [ 95.315136] [<0000b273>] (show_stack) from [<00092455>] (sysfs_warn_dup+0x31/0x48) [ 95.323247] [<00092455>] (sysfs_warn_dup) from [<00092635>] (sysfs_do_create_link_sd+0x75/0x88) [ 95.332539] [<00092635>] (sysfs_do_create_link_sd) from [<00125823>] (device_add+0x133/0x3b0) [ 95.341694] [<00125823>] (device_add) from [<001059ed>] (export_store+0xb5/0x12c) [ 95.349761] [<001059ed>] (export_store) from [<00091911>] (kernfs_fop_write+0x87/0xda) [ 95.358150] [<00091911>] (kernfs_fop_write) from [<0005beb1>] (__vfs_write+0x1d/0xe0) [ 95.366295] [<0005beb1>] (__vfs_write) from [<0005bfe7>] (vfs_write+0x4f/0x7c) [ 95.374053] [<0005bfe7>] (vfs_write) from [<0005c0bf>] (ksys_write+0x33/0x70) [ 95.381708] [<0005c0bf>] (ksys_write) from [<00009001>] (ret_fast_syscall+0x1/0x58) [ 95.389682] Exception stack(0x01bcffa8 to 0x01bcfff0) [ 95.394946] ffa0: 00000000 00c4883c 00000001 00c4e590 00000002 00000004 [ 95.403639] ffc0: 00000000 00c4883c 00c4cbe8 00000004 00000002 00000020 00000000 00c4d008 [ 95.412223] ffe0: 00c29151 00c4cbe8 00c17833 00c13c0c -sh: write error: File exists [1] https://lkml.org/lkml/2018/9/25/713 [2] https://lkml.org/lkml/2018/9/25/447 --- Changes in v2: - update revert commit message - new patch 2/2 to propose uevent notification (change) on pwmchip Fabrice Gasnier (2): Revert "pwm: Set class for exported channels in sysfs" pwm: send a uevent on the pwmchip device upon channel sysfs (un)export drivers/pwm/sysfs.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)