[Outreachy kernel] [PATCH v13 2/3] drm/tinydrm: Move tinydrm_of_find_backlight to backlight.c
Sean Paul
seanpaul at chromium.org
Mon Oct 16 18:31:49 UTC 2017
On Fri, Oct 13, 2017 at 7:25 PM, Rob Clark <robdclark at gmail.com> wrote:
> On Fri, Oct 13, 2017 at 4:25 PM, Sean Paul <seanpaul at chromium.org> wrote:
>> On Fri, Oct 13, 2017 at 04:11:43PM +0530, Meghana Madhyastha wrote:
>>> Rename tinydrm_of_find_backlight to backlight_get and move it
>>> to linux/backlight.c so that it can be used by other drivers.
>>
>> [apologies if this has been brought up in previous versions, I haven't been
>> following closely]
>>
>> I don't think "backlight_get" is a good name for this function. How about
>> of_find_backlight_by_name (since there's already of_find_backlight_by_node)?
>>
>>>
>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha at gmail.com>
>>> ---
>>> Changes in v13:
>>> -Add backlight_put to backlight.h in this patch
>>>
>>> drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 --------------------------
>>> drivers/gpu/drm/tinydrm/mi0283qt.c | 3 +-
>>> drivers/video/backlight/backlight.c | 37 ++++++++++++++++++++++++
>>> include/drm/tinydrm/tinydrm-helpers.h | 2 --
>>> include/linux/backlight.h | 19 ++++++++++++
>>> 5 files changed, 58 insertions(+), 43 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>> index a42dee6..cb1a01a 100644
>>> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>> @@ -236,46 +236,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>> }
>>> EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>>>
>>> -/**
>>> - * tinydrm_of_find_backlight - Find backlight device in device-tree
>>> - * @dev: Device
>>> - *
>>> - * This function looks for a DT node pointed to by a property named 'backlight'
>>> - * and uses of_find_backlight_by_node() to get the backlight device.
>>> - * Additionally if the brightness property is zero, it is set to
>>> - * max_brightness.
>>> - *
>>> - * Returns:
>>> - * NULL if there's no backlight property.
>>> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>> - * is found.
>>> - * If the backlight device is found, a pointer to the structure is returned.
>>> - */
>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
>>> -{
>>> - struct backlight_device *backlight;
>>> - struct device_node *np;
>>> -
>>> - np = of_parse_phandle(dev->of_node, "backlight", 0);
>>> - if (!np)
>>> - return NULL;
>>> -
>>> - backlight = of_find_backlight_by_node(np);
>>> - of_node_put(np);
>>> -
>>> - if (!backlight)
>>> - return ERR_PTR(-EPROBE_DEFER);
>>> -
>>> - if (!backlight->props.brightness) {
>>> - backlight->props.brightness = backlight->props.max_brightness;
>>> - DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>> - backlight->props.brightness);
>>> - }
>>> -
>>> - return backlight;
>>> -}
>>> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
>>> -
>>> #if IS_ENABLED(CONFIG_SPI)
>>>
>>> /**
>>> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>> index 7fd2691..a932185 100644
>>> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
>>> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>> @@ -12,6 +12,7 @@
>>> #include <drm/tinydrm/ili9341.h>
>>> #include <drm/tinydrm/mipi-dbi.h>
>>> #include <drm/tinydrm/tinydrm-helpers.h>
>>> +#include <linux/backlight.h>
>>> #include <linux/delay.h>
>>> #include <linux/gpio/consumer.h>
>>> #include <linux/module.h>
>>> @@ -188,7 +189,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>>> if (IS_ERR(mipi->regulator))
>>> return PTR_ERR(mipi->regulator);
>>>
>>> - mipi->backlight = tinydrm_of_find_backlight(dev);
>>> + mipi->backlight = backlight_get(dev);
>>> if (IS_ERR(mipi->backlight))
>>> return PTR_ERR(mipi->backlight);
>>>
>>> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
>>> index 8049e76..c4e94d0 100644
>>> --- a/drivers/video/backlight/backlight.c
>>> +++ b/drivers/video/backlight/backlight.c
>>> @@ -580,6 +580,43 @@ struct backlight_device *of_find_backlight_by_node(struct device_node *node)
>>> EXPORT_SYMBOL(of_find_backlight_by_node);
>>> #endif
>>>
>>> +/**
>>> + * backlight_get - Get backlight device
>>> + * @dev: Device
>>> + *
>>> + * This function looks for a property named 'backlight' on the DT node
>>> + * connected to @dev and looks up the backlight device.
>>> + *
>>> + * Call backlight_put() to drop the reference on the backlight device.
>>> + *
>>> + * Returns:
>>> + * A pointer to the backlight device if found.
>>> + * Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
>>> + * device is found.
>>> + * NULL if there's no backlight property.
>>> + */
>>> +struct backlight_device *backlight_get(struct device *dev)
>>> +{
>>> + struct backlight_device *bd = NULL;
>>> + struct device_node *np;
>>> +
>>> + if (!dev)
>>> + return NULL;
>>> +
>>> + if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
>>
>> I'm not really used to seeing IS_ENABLED(CONFIG_BLAH) inline. The common
>> patterns seems to be wrapping the actual implementation in #if
>> IS_ENABLED(CONFIG_BLAH) and then sticking a stub implementation in the #else.
>
>
> drive-by comment, but I actually prefer 'if (IS_ENABLED(CONFIG_FOO))
> ..' when possible.. it keeps the code compiled by the front-end of the
> compiler in more configs so less likely to bitrot, and the compiler is
> plenty good at DCE to eliminate the code when disabled in later stages
> of the compiler..
>
Sounds reasonable. I think there is already a stub implementation for
this function, so it's a little awkward gating on one CONFIG and not
another. Given Noralf's idea that backlight_get() be a general purpose
accessor, it makes a bit more sense to gate the entire function on
CONFIG_BACKLIGHT_CLASS_DRIVER and only a portion on CONFIG_OF.
So, I guess I'm fine with leaving this here.
Sean
> possibly exceptions are things that are called frequently where you
> want to inline the CONFIG_FOO=n stub so it can be eliminated without
> calling into another object file (at least until LTO gets good), but I
> guess that is not the case here..
>
> BR,
> -R
>
>
>> I see below that you already have a stub if backlight is not enabled, so expand
>> that #if to include CONFIG_OF as well.
>>
>>> + np = of_parse_phandle(dev->of_node, "backlight", 0);
>>> + if (np) {
>>> + bd = of_find_backlight_by_node(np);
>>> + of_node_put(np);
>>> + if (!bd)
>>> + return ERR_PTR(-EPROBE_DEFER);
>>> + }
>>> + }
>>> +
>>> + return bd;
>>> +}
>>> +EXPORT_SYMBOL(backlight_get);
>>> +
>>> static void __exit backlight_class_exit(void)
>>> {
>>> class_destroy(backlight_class);
>>> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
>>> index f54fae0..0a4ddbc 100644
>>> --- a/include/drm/tinydrm/tinydrm-helpers.h
>>> +++ b/include/drm/tinydrm/tinydrm-helpers.h
>>> @@ -46,8 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>>> void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>> struct drm_clip_rect *clip);
>>>
>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>>> -
>>> size_t tinydrm_spi_max_transfer_size(struct spi_device *spi, size_t max_len);
>>> bool tinydrm_spi_bpw_supported(struct spi_device *spi, u8 bpw);
>>> int tinydrm_spi_transfer(struct spi_device *spi, u32 speed_hz,
>>> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
>>> index b88fabb..987a6d7 100644
>>> --- a/include/linux/backlight.h
>>> +++ b/include/linux/backlight.h
>>> @@ -159,6 +159,16 @@ static inline int backlight_disable(struct backlight_device *bd)
>>> return backlight_update_status(bd);
>>> }
>>>
>>> +/**
>>> + * backlight_put - Drop backlight reference
>>> + * @bd: the backlight device to put
>>> + */
>>> +static inline void backlight_put(struct backlight_device *bd)
>>> +{
>>> + if (bd)
>>> + put_device(&bd->dev);
>>> +}
>>
>> I'm not convinced this function needs to exist.
>>
>>> +
>>> extern struct backlight_device *backlight_device_register(const char *name,
>>> struct device *dev, void *devdata, const struct backlight_ops *ops,
>>> const struct backlight_properties *props);
>>> @@ -202,4 +212,13 @@ of_find_backlight_by_node(struct device_node *node)
>>> }
>>> #endif
>>>
>>> +#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
>>> +struct backlight_device *backlight_get(struct device *dev);
>>> +#else
>>> +static inline struct backlight_device *backlight_get(struct device *dev)
>>> +{
>>> + return NULL;
>>> +}
>>> +#endif
>>> +
>>> #endif
>>> --
>>> 2.7.4
>>>
>>> --
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>>
>> --
>> Sean Paul, Software Engineer, Google / Chromium OS
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