linux-stable.git/drivers/video/backlight, branch linux-5.17.y

backlight: qcom-wled: Respect enabled-strings in set_brightness

2021-12-22T11:18:46+00:00

The hardware is capable of controlling any non-contiguous sequence of
LEDs specified in the DT using qcom,enabled-strings as u32
array, and this also follows from the DT-bindings documentation.  The
numbers specified in this array represent indices of the LED strings
that are to be enabled and disabled.

Its value is appropriately used to setup and enable string modules, but
completely disregarded in the set_brightness paths which only iterate
over the number of strings linearly.
Take an example where only string 2 is enabled with
qcom,enabled_strings=<2>: this string is appropriately enabled but
subsequent brightness changes would have only touched the zero'th
brightness register because num_strings is 1 here.  This is simply
addressed by looking up the string for this index in the enabled_strings
array just like the other codepaths that iterate over num_strings.

Likewise enabled_strings is now also used in the autodetection path for
consistent behaviour: when a list of strings is specified in DT only
those strings will be probed for autodetection, analogous to how the
number of strings that need to be probed is already bound by
qcom,num-strings.  After all autodetection uses the set_brightness
helpers to set an initial value, which could otherwise end up changing
brightness on a different set of strings.

Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
Fixes: 03b2b5e86986 ("backlight: qcom-wled: Add support for WLED4 peripheral")
Signed-off-by: Marijn Suijten 
Reviewed-by: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-10-marijn.suijten@somainline.org

backlight: qcom-wled: Remove unnecessary double whitespace

2021-12-22T11:18:24+00:00

Remove redundant spaces inside for loop conditions.  No other double
spaces were found that are not part of indentation with `[^\s]  `.

Signed-off-by: Marijn Suijten 
Reviewed-by: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-9-marijn.suijten@somainline.org

backlight: qcom-wled: Provide enabled_strings default for WLED 4 and 5

2021-12-22T11:18:02+00:00

Only WLED 3 sets a sensible default that allows operating this driver
with just qcom,num-strings in the DT; WLED 4 and 5 require
qcom,enabled-strings to be provided otherwise enabled_strings remains
zero-initialized, resulting in every string-specific register write
(currently only the setup and config functions, brightness follows in a
future patch) to only configure the zero'th string multiple times.

Signed-off-by: Marijn Suijten 
Reviewed-by: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-8-marijn.suijten@somainline.org

backlight: qcom-wled: Remove unnecessary 4th default string in WLED3

2021-12-22T11:17:35+00:00

The previous commit improves num_strings parsing to not go over the
maximum of 3 strings for WLED3 anymore.  Likewise this default index for
a hypothetical 4th string is invalid and could access registers that are
not mapped to the desired purpose.
Removing this value gets rid of undesired confusion and avoids the
possibility of accessing registers at this offset even if the 4th array
element is used by accident.

Signed-off-by: Marijn Suijten 
Reviewed-by: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-7-marijn.suijten@somainline.org

backlight: qcom-wled: Override default length with qcom,enabled-strings

2021-12-22T11:17:13+00:00

The length of qcom,enabled-strings as property array is enough to
determine the number of strings to be enabled, without needing to set
qcom,num-strings to override the default number of strings when less
than the default (which is also the maximum) is provided in DT.

This also introduces an extra warning when qcom,num-strings is set,
denoting that it is not necessary to set both anymore.  It is usually
more concise to set just qcom,num-length when a zero-based, contiguous
range of strings is needed (the majority of the cases), or to only set
qcom,enabled-strings when a specific set of indices is desired.

Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
Signed-off-by: Marijn Suijten 
Reviewed-by: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-6-marijn.suijten@somainline.org

backlight: qcom-wled: Fix off-by-one maximum with default num_strings

2021-12-22T11:16:33+00:00

When not specifying num-strings in the DT the default is used, but +1 is
added to it which turns WLED3 into 4 and WLED4/5 into 5 strings instead
of 3 and 4 respectively, causing out-of-bounds reads and register
read/writes.  This +1 exists for a deficiency in the DT parsing code,
and is simply omitted entirely - solving this oob issue - by parsing the
property separately much like qcom,enabled-strings.

This also enables more stringent checks on the maximum value when
qcom,enabled-strings is provided in the DT, by parsing num-strings after
enabled-strings to allow it to check against (and in a subsequent patch
override) the length of enabled-strings: it is invalid to set
num-strings higher than that.
The DT currently utilizes it to get around an incorrect fixed read of
four elements from that array (has been addressed in a prior patch) by
setting a lower num-strings where desired.

Fixes: 93c64f1ea1e8 ("leds: add Qualcomm PM8941 WLED driver")
Signed-off-by: Marijn Suijten 
Reviewed-By: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-5-marijn.suijten@somainline.org

backlight: qcom-wled: Use cpu_to_le16 macro to perform conversion

2021-12-22T11:16:02+00:00

The kernel already provides appropriate primitives to perform endianness
conversion which should be used in favour of manual bit-wrangling.

Signed-off-by: Marijn Suijten 
Reviewed-by: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-4-marijn.suijten@somainline.org

backlight: qcom-wled: Pass number of elements to read to read_u32_array

2021-12-22T11:15:35+00:00

of_property_read_u32_array takes the number of elements to read as last
argument. This does not always need to be 4 (sizeof(u32)) but should
instead be the size of the array in DT as read just above with
of_property_count_elems_of_size.

To not make such an error go unnoticed again the driver now bails
accordingly when of_property_read_u32_array returns an error.
Surprisingly the indentation of newlined arguments is lining up again
after prepending `rc = `.

Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
Signed-off-by: Marijn Suijten 
Reviewed-by: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-3-marijn.suijten@somainline.org

backlight: qcom-wled: Validate enabled string indices in DT

2021-12-22T11:14:46+00:00

The strings passed in DT may possibly cause out-of-bounds register
accesses and should be validated before use.

Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
Signed-off-by: Marijn Suijten 
Reviewed-by: AngeloGioacchino Del Regno 
Reviewed-by: Daniel Thompson 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211115203459.1634079-2-marijn.suijten@somainline.org

backlight: lp855x: Add support ACPI enumeration

2021-12-22T11:14:14+00:00

The Xiaomi Mi Pad 2 tablet uses an ACPI enumerated LP8556 backlight
controller for its LCD-panel, with a Xiaomi specific ACPI HID of
"XMCC0001", add support for this.

Note the new "if (id)" check also fixes a NULL pointer deref when a user
tries to manually bind the driver from sysfs.

When CONFIG_ACPI is disabled acpi_match_device() will always return NULL,
so the lp855x_parse_acpi() call will get optimized away.

Reviewed-by: Daniel Thompson 
Signed-off-by: Hans de Goede 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20211102225504.18920-3-hdegoede@redhat.com