Den 01.10.2017 15.34, skrev Meghana Madhyastha:
> On Sun, Oct 01, 2017 at 03:26:36PM +0200, Noralf Trønnes wrote:
>> Den 01.10.2017 06.14, skrev Meghana Madhyastha:
>>> On Sat, Sep 30, 2017 at 09:04:57PM +0200, Noralf Trønnes wrote:
>>>> Den 30.09.2017 19.12, skrev Meghana Madhyastha:
>>>>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>>>>> and move it into drm_of.c from tinydrm-helpers.c. This is
>>>>> because other drivers in the drm subsystem might need to call
>>>>> this function. In that case and otherwise, it is better from
>>>>> an organizational point of view to move it into drm_of.c along
>>>>> with the other _of.c functions.
>>>>>
>>>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha at gmail.com>
>>>>> ---
>>>>> Changes in v6:
>>>>> -Move function declarations to linux/backlight.h to resolve
>>>>> module dependency issues.
>>>>>
>>>>> drivers/gpu/drm/drm_of.c | 44 ++++++++++++++++++++++++++
>>>>> drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>>>> drivers/gpu/drm/tinydrm/mi0283qt.c | 2 +-
>>>>> include/drm/tinydrm/tinydrm-helpers.h | 1 -
>>>>> include/linux/backlight.h | 11 +++++++
>>>>> 5 files changed, 56 insertions(+), 42 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>>>> index 8dafbdf..d878d3a 100644
>>>>> --- a/drivers/gpu/drm/drm_of.c
>>>>> +++ b/drivers/gpu/drm/drm_of.c
>>>>> @@ -1,6 +1,7 @@
>>>>> #include <linux/component.h>
>>>>> #include <linux/export.h>
>>>>> #include <linux/list.h>
>>>>> +#include <linux/backlight.h>
>>>>> #include <linux/of_graph.h>
>>>>> #include <drm/drmP.h>
>>>>> #include <drm/drm_bridge.h>
>>>>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>> return ret;
>>>>> }
>>>>> EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>>>>> +
>>>>> +/**
>>>>> + * drm_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.
>>>>> + *
>>>>> + * Note: It is the responsibility of the caller to call put_device() when
>>>>> + * releasing the resource.
>>>>> + *
>>>>> + * 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 *drm_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(drm_of_find_backlight);
>>>>> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>> index bd6cce0..cd4c6a5 100644
>>>>> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>> @@ -237,46 +237,6 @@ 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);
>>>>> -
>>>>> -/**
>>>>> * tinydrm_enable_backlight - Enable backlight helper
>>>>> * @backlight: Backlight device
>>>>> *
>>>>> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>> index 7e5bb7d..682b4db 100644
>>>>> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>> @@ -189,7 +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 = drm_of_find_backlight(dev);
>>>>> if (IS_ERR(mipi->backlight))
>>>>> return PTR_ERR(mipi->backlight);
>>>>> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
>>>>> index d554ded..e40ef2d 100644
>>>>> --- a/include/drm/tinydrm/tinydrm-helpers.h
>>>>> +++ b/include/drm/tinydrm/tinydrm-helpers.h
>>>>> @@ -46,7 +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);
>>>>> int tinydrm_enable_backlight(struct backlight_device *backlight);
>>>>> int tinydrm_disable_backlight(struct backlight_device *backlight);
>>>>> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
>>>>> index 5f2fd61..47a095e 100644
>>>>> --- a/include/linux/backlight.h
>>>>> +++ b/include/linux/backlight.h
>>>>> @@ -172,4 +172,15 @@ of_find_backlight_by_node(struct device_node *node)
>>>>> }
>>>>> #endif
>>>>> +#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
>>>>> +struct backlight_device *
>>>>> +drm_of_find_backlight(struct device *dev);
>>>>> +#else
>>>>> +static inline struct backlight_device *
>>>>> +drm_of_find_backlight(struct device *dev)
>>>>> +{
>>>>> + return NULL;
>>>>> +}
>>>>> +#endif
>>>>> +
>>>>> #endif
>>>> This isn't what I meant, you only change the of_find_backlight_by_node()
>>>> declaration/definition. It should be like this:
>>>>
>>>> #if defined(CONFIG_OF) && IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
>>>> struct backlight_device *of_find_backlight_by_node(struct device_node
>>>> *node);
>>>> #else
>>>> static inline struct backlight_device *
>>>> of_find_backlight_by_node(struct device_node *node)
>>>> {
>>>> return NULL;
>>>> }
>>>> #endif
>>> I see. So basically add the function declaration of drm_of_find_backlight
>>> and devm_drm_of_find_backlight in drm_of.h and this function declaration
>>> need not be inside the #ifdef CONFIG / #else part?
>>> So there need not be a dummy version of drm_of_find_backlight here
>>> because we are anyway taking care of that in of_find_backliht by node?
>>> Sorry for the many versions and thank you for the clarifications.
>> You need the dummy part in drm_of.h because you need to handle the
>> CONFIG_OF option here as well.
>>
>> If drm_of_find_backlight() was only 2-3 lines of code, you could have
>> made a static inline function in drm_of.h outside the #if/#else/#endif,
>> but since it's longer than that it should be in drm_of.c.
>>
>> CONFIG_OF decides if drm_of.c is built (as part of drm.o) or not:
>>
>> drivers/gpu/drm/Makefile:
>> drm-$(CONFIG_OF) += drm_of.o
>>
>> This means we need a function prototype declaration for the CONFIG_OF=y
>> case, and an inline function definition for the CONFIG_OF=n case.
>>
>> Noralf.
> I have one more question. In that case, why wouldn't my previous patch
> work ? (i.e definition and declaration of drm_of_find_backlight
> in linux/backlight.h with if/else directives)
It will work, the compiler doesn't complain as long as you include
backlight.h and make sure drm_of.c is built. But that would result
in a complexity that humans would struggle to get right. And in this
case it's even 2 different subsystems with different maintainers...
So in order to succeed with complex projects, humans need some more
rules than what the compiler requires. And one of those are:
A header file is usually connected to a source file.
backlight.h contains prototypes and definitions for backlight.c
drm_of.h contains prototypes and definitions for drm_of.c
> Regards,
> Meghana
>
>>> Regards,
>>> Meghana
>>>> And this change needs to be a patch on it's own. The backlight subsystem
>>>> has it's own maintainer that will review this change.
>>>> It's best to send him/them the whole patchset so they see the context.
>>>>
>>>> Noralf.
>>>>