media: atomisp: Add v4l2_get_acpi_sensor_info() helper

ACPI nodes describing sensors on atomisp devices implement a
"79234640-9e10-4fea-a5c1-b5aa8b19756f" Device Specific Method (DSM)
to get info about the GPIOs.

Using this method is necessary to figure out which ACPI GPIO resource
is "reset" and which one is "powerdown" and this is also necessary to
figure out the correct polarity of the pins.

One example where this is necessary is the GC0310 sensor. The current
GC0310 code hardcodes reset as being active-low and power-down as being
active-high. This works on a number of devices such as the mpman
converter 9. But it is wrong for the Chuwi Vi8 CWI501 where the powerdown
pin is active-low.

Rather then adding DMI quirks for this, add a helper for this,
which can be shared between sensor-drivers. This new helper optionally
also returns a string identifying the exact sensor-module used, which
might be useful if any module specific behvior is necessary in the sensor
driver.

This uses the DSM directly on the sensor device's ACPI node. This is
different from later Intel hardware (IPU3 / IPU6) which has a separate
INT3472 node (with its own driver) with this info.

Since there is no separate ACPI node to which we can bind to register GPIO
lookups, this unfortunately means that all sensor drivers which may be used
on BYT or CHT hw need to call this new helper.

Note for now this function is being added to atomisp_gmin_platform.c,
but once things are ready to move atomisp over to using generic sensor
drivers this will need to become a generic v4l2 sensor helper. but this
will require upstream discussion first.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/staging/media/atomisp/include/linux/atomisp_platform.h b/drivers/staging/media/atomisp/include/linux/atomisp_platform.h
index b77bf814a5a6..e8e965f73fc8 100644
--- a/drivers/staging/media/atomisp/include/linux/atomisp_platform.h
+++ b/drivers/staging/media/atomisp/include/linux/atomisp_platform.h
@@ -213,6 +213,8 @@ int atomisp_register_sensor_no_gmin(struct v4l2_subdev *subdev, u32 lanes,
 				    enum atomisp_bayer_order bayer_order);
 void atomisp_unregister_subdev(struct v4l2_subdev *subdev);
 
+int v4l2_get_acpi_sensor_info(struct device *dev, char **module_id_str);
+
 /* API from old platform_camera.h, new CPUID implementation */
 #define __IS_SOC(x) (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && \
 		     boot_cpu_data.x86 == 6 &&                       \