[Outreachy kernel] [PATCH v14 2/3] drm/tinydrm: Move tinydrm_of_find_backlight to backlight.c
Daniel Thompson
daniel.thompson at linaro.org
Tue Oct 24 15:56:59 UTC 2017
On 24/10/17 16:38, Sean Paul wrote:
> On Sat, Oct 21, 2017 at 05:27:33PM +0530, Meghana Madhyastha wrote:
>> Rename tinydrm_of_find_backlight to of_find_backlight and move
>> it to linux/backlight.c so that it can be used by other drivers.
>>
>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha at gmail.com>
>> ---
>> Changes in v14:
>> -s/backlight_get/of_find_backlight/
>>
>> 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..53ab5a0 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 = of_find_backlight(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..76d46c3 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
>>
>> +/**
>> + * of_find_backlight - 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 *of_find_backlight(struct device *dev)
>> +{
>> + struct backlight_device *bd = NULL;
>> + struct device_node *np;
>> +
>> + if (!dev)
>> + return NULL;
>> +
>> + if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
>> + 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(of_find_backlight);
>> +
>> 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..f98b684 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);
>> +}
>
>
> As I mentioned in my last review, I don't think we need this function.
Just to check... some DRM drivers do allow themselves to work if
CONFIG_BACKLIGHT_CLASS_DEVICE isn't enabled (as discussed earlier in the
thread ;-). Did you consider what happens when this happens.
Wrapped up with backlight_put() we are sure never to accidentally
dereference bd in DRM de-init paths when CONFIG_BACKLIGHT_CLASS_DEVICVE
if it is not set. With a raw put_device() all that conditional logic
ends up on the driver.
Daniel.
>> +
>> 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 *of_find_backlight(struct device *dev);
>> +#else
>> +static inline struct backlight_device *of_find_backlight(struct device *dev)
>> +{
>> + return NULL;
>> +}
>> +#endif
>> +
>> #endif
>> --
>> 2.7.4
>>
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>
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