linux-kernel - Re: [PATCH v3 1/2] drm/dsi: Implement dcs set/get display brightness

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Date:	Tue, 19 Jul 2016 05:49:24 -0400
From:	Sean Paul <seanpaul@...gle.com>
To:	Vinay Simha <simhavcs@...il.com>
Cc:	John Stultz <john.stultz@...aro.org>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Archit Taneja <archit.taneja@...il.com>,
	Rob Clark <robdclark@...il.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Emil Velikov <emil.l.velikov@...il.com>,
	David Airlie <airlied@...ux.ie>,
	"open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] drm/dsi: Implement dcs set/get display brightness

On Tue, Jul 19, 2016 at 5:42 AM, Vinay Simha <simhavcs@...il.com> wrote:
> just to be inline with the existing code (funcs:
> mipi_dsi_dcs_get_power_mode, mipi_dsi_dcs_get_pixel_format) in
> drivers/gpu/drm/drm_mipi_dsi.c followed the same for
> mipi_dsi_dcs_get_display_brightness
>
> We may need to change as you suggested for other two functions also.
> please suggest.
>

Ah, didn't see that. I don't really care either way, tbh, just
something that struck me as odd. Feel free to ignore.

Sean


>
>
>
> On Tue, Jul 19, 2016 at 3:00 PM, Sean Paul <seanpaul@...gle.com> wrote:
>> On Mon, Jul 18, 2016 at 4:28 AM, Vinay Simha BN <simhavcs@...il.com> wrote:
>>> Provide a small convenience wrapper that set/get the
>>> display brightness value
>>>
>>> Cc: John Stultz <john.stultz@...aro.org>
>>> Cc: Sumit Semwal <sumit.semwal@...aro.org>
>>> Cc: Archit Taneja <archit.taneja@...il.com>
>>> Cc: Rob Clark <robdclark@...il.com>
>>> Cc: Jani Nikula <jani.nikula@...ux.intel.com>
>>> Cc: Thierry Reding <thierry.reding@...il.com>
>>> Cc: Emil Velikov <emil.l.velikov@...il.com>
>>> Signed-off-by: Vinay Simha BN <simhavcs@...il.com>
>>>
>>> ---
>>> v1:
>>>  *tested in nexus7 2nd gen.
>>>
>>> v2:
>>>  * implemented jani review comments
>>>    -functions name mapped accordingly
>>>    -bl value increased from 0xff to 0xffff
>>>    -backlight interface will be handled in panel driver,
>>>     so it is moved from the mipi_dsi helper function
>>>
>>> v3:
>>>  * emil review comments
>>>    (err < 0) supposed to be (err <= 0)
>>> ---
>>>  drivers/gpu/drm/drm_mipi_dsi.c | 49 ++++++++++++++++++++++++++++++++++++++++++
>>>  include/drm/drm_mipi_dsi.h     |  4 ++++
>>>  2 files changed, 53 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
>>> index af0d471..43aa743 100644
>>> --- a/drivers/gpu/drm/drm_mipi_dsi.c
>>> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
>>> @@ -1041,6 +1041,55 @@ int mipi_dsi_dcs_set_pixel_format(struct mipi_dsi_device *dsi, u8 format)
>>>  }
>>>  EXPORT_SYMBOL(mipi_dsi_dcs_set_pixel_format);
>>>
>>> +/**
>>> + * mipi_dsi_dcs_get_display_brightness() - gets the current brightness value
>>> + * of the display
>>> + * @dsi: DSI peripheral device
>>> + * @brightness: brightness value
>>> + *
>>> + * Return: 0 on success or a negative error code on failure.
>>> + */
>>> +int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
>>> +                                       u16 *brightness)
>>> +{
>>> +       ssize_t err;
>>> +
>>> +       err = mipi_dsi_dcs_read(dsi, MIPI_DCS_GET_DISPLAY_BRIGHTNESS,
>>> +                               brightness, sizeof(*brightness));
>>> +       if (err <= 0) {
>>> +               if (err == 0)
>>> +                       err = -ENODATA;
>>> +
>>> +               return err;
>>> +       }
>>> +
>>> +       return 0;
>>
>> IMO, this is still pretty awkward. I think the following is a bit more
>> conventional:
>>
>> err = mipi_dsi_dcs_...
>> if (err == 0)
>>     return -ENODATA;
>> else if (err < 0)
>>     return err;
>>
>> return 0;
>>
>>> +}
>>> +EXPORT_SYMBOL(mipi_dsi_dcs_get_display_brightness);
>>> +
>>> +/**
>>> + * mipi_dsi_dcs_set_display_brightness() - sets the brightness value of
>>> + * the display
>>> + * @dsi: DSI peripheral device
>>> + * @brightness: brightness value
>>> + *
>>> + * Return: 0 on success or a negative error code on failure.
>>> + */
>>> +int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
>>> +                                       u16 brightness)
>>> +{
>>> +       ssize_t err;
>>> +       u8 bl_value[2] = { brightness & 0xff, brightness >> 8 };
>>> +
>>> +       err = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
>>> +                                bl_value, sizeof(bl_value));
>>> +       if (err < 0)
>>> +               return err;
>>> +
>>> +       return 0;
>>> +}
>>> +EXPORT_SYMBOL(mipi_dsi_dcs_set_display_brightness);
>>> +
>>>  static int mipi_dsi_drv_probe(struct device *dev)
>>>  {
>>>         struct mipi_dsi_driver *drv = to_mipi_dsi_driver(dev->driver);
>>> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
>>> index 47ac925..404c373 100644
>>> --- a/include/drm/drm_mipi_dsi.h
>>> +++ b/include/drm/drm_mipi_dsi.h
>>> @@ -270,6 +270,10 @@ int mipi_dsi_dcs_set_tear_off(struct mipi_dsi_device *dsi);
>>>  int mipi_dsi_dcs_set_tear_on(struct mipi_dsi_device *dsi,
>>>                              enum mipi_dsi_dcs_tear_mode mode);
>>>  int mipi_dsi_dcs_set_pixel_format(struct mipi_dsi_device *dsi, u8 format);
>>> +int mipi_dsi_dcs_get_display_brightness(struct mipi_dsi_device *dsi,
>>> +                                       u16 *brightness);
>>> +int mipi_dsi_dcs_set_display_brightness(struct mipi_dsi_device *dsi,
>>> +                                       u16 brightness);
>>>
>>>  /**
>>>   * struct mipi_dsi_driver - DSI driver
>>> --
>>> 2.1.2
>>>
>
>
>
> --
> Regards,
>
> Vinay Simha.B.N.