[v3,0/9] backlight: qcom-wled: fix and solidify handling of enabled-strings

This patchset fixes WLED's handling of enabled-strings: besides some
cleanup it is now actually possible to specify a non-contiguous array of
enabled strings (not necessarily starting at zero) and the values from
DT are now validated to prevent possible unexpected out-of-bounds
register and array element accesses.
Off-by-one mistakes in the maximum number of strings, also causing
out-of-bounds access, have been addressed as well.

Changes in v3:
- Use __le16 type for cpu_to_le16 result;
- Reword ambiguity warning between qcom,num-strings and
  qcom,enabled-strings to explain that only one should/needs to be set;
- Move this warning from patch 4 patch 5, where the length of
  qcom,enabled-strings starts to be taken into account;
- Drop DT patches that have been picked up in the qcom tree.

v2: https://lore.kernel.org/lkml/20211112002706.453289-1-marijn.suijten@somainline.org/T

Changes in v2:
- Reordered patch 4/10 (Validate enabled string indices in DT) to sit
  before patch 1/10 (Pass number of elements to read to read_u32_array);
- Pulled qcom,num-strings out of the DT enumeration parser, and moved it
  after qcom,enabled-strings parser to always have final sign-off over
  the number of strings;
- Extra validation for this number of strings against
  qcom,enabled-strings;
- Recombined patch 9 (Consistently use enabled-strings in
  set_brightness) and patch 10 (Consider enabled_strings in
  autodetection), which both solve the same problem in two different
  functions.  In addition the autodetection code uses set_brightness as
  helper already;
- Improved DT configurations for pmi8994 and pm660l, currently in 5.15
  rc's.

v1: https://lore.kernel.org/dri-devel/20211004192741.621870-1-marijn.suijten@somainline.org/T

Marijn Suijten (9):
  backlight: qcom-wled: Validate enabled string indices in DT
  backlight: qcom-wled: Pass number of elements to read to
    read_u32_array
  backlight: qcom-wled: Use cpu_to_le16 macro to perform conversion
  backlight: qcom-wled: Fix off-by-one maximum with default num_strings
  backlight: qcom-wled: Override default length with
    qcom,enabled-strings
  backlight: qcom-wled: Remove unnecessary 4th default string in WLED3
  backlight: qcom-wled: Provide enabled_strings default for WLED 4 and 5
  backlight: qcom-wled: Remove unnecessary double whitespace
  backlight: qcom-wled: Respect enabled-strings in set_brightness

 drivers/video/backlight/qcom-wled.c | 130 +++++++++++++++-------------
 1 file changed, 72 insertions(+), 58 deletions(-)


base-commit: fa55b7dcdc43c1aa1ba12bca9d2dd4318c2a0dbf
--
2.33.1

On 2021-11-16 15:42:15, Lee Jones wrote:
> On Tue, 16 Nov 2021, Daniel Thompson wrote:
> 
> > Hi Lee
> > 
> > On Mon, Nov 15, 2021 at 09:34:50PM +0100, Marijn Suijten wrote:
> > > This patchset fixes WLED's handling of enabled-strings: besides some
> > > cleanup it is now actually possible to specify a non-contiguous array of
> > > enabled strings (not necessarily starting at zero) and the values from
> > > DT are now validated to prevent possible unexpected out-of-bounds
> > > register and array element accesses.
> > > Off-by-one mistakes in the maximum number of strings, also causing
> > > out-of-bounds access, have been addressed as well.
> > 
> > They have arrived piecemeal (during v1, v2 and v3) but all patches on
> > the set should now have my R-b: attached to them.
> 
> I can see that.  Nothing for you to worry about.
> 
> I'll apply these when I conduct my next sweep, thanks.

Thanks for that Lee!  Has the next sweep already passed by?  Seems
everyone is preparing for the 5.17 merge window but these patches
haven't yet landed on the backlight tree [1].  I'd appreciate it if we
can make them appear in the 5.17 window :)

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight.git/

Thanks!
- Marijn

> -- 
> Lee Jones [李琼斯]
> Senior Technical Lead - Developer Services
> Linaro.org │ Open source software for Arm SoCs
> Follow Linaro: Facebook | Twitter | Blog

On Wed, 22 Dec 2021, Marijn Suijten wrote:

> On 2021-11-16 15:42:15, Lee Jones wrote:
> > On Tue, 16 Nov 2021, Daniel Thompson wrote:
> > 
> > > Hi Lee
> > > 
> > > On Mon, Nov 15, 2021 at 09:34:50PM +0100, Marijn Suijten wrote:
> > > > This patchset fixes WLED's handling of enabled-strings: besides some
> > > > cleanup it is now actually possible to specify a non-contiguous array of
> > > > enabled strings (not necessarily starting at zero) and the values from
> > > > DT are now validated to prevent possible unexpected out-of-bounds
> > > > register and array element accesses.
> > > > Off-by-one mistakes in the maximum number of strings, also causing
> > > > out-of-bounds access, have been addressed as well.
> > > 
> > > They have arrived piecemeal (during v1, v2 and v3) but all patches on
> > > the set should now have my R-b: attached to them.
> > 
> > I can see that.  Nothing for you to worry about.
> > 
> > I'll apply these when I conduct my next sweep, thanks.
> 
> Thanks for that Lee!  Has the next sweep already passed by?  Seems
> everyone is preparing for the 5.17 merge window but these patches
> haven't yet landed on the backlight tree [1].  I'd appreciate it if we
> can make them appear in the 5.17 window :)

No need to panic.

v5.17-rc1 isn't due to be cut for either 3.5 or 4.5 weeks.