On Sun, Oct 01, 2017 at 04:47:26PM +0200, Noralf Trønnes wrote:
>
> 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@xxxxxxxxx>
> >>>>>---
> >>>>>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
Okay that makes sense. Initially, I thought that we could add the
declarations/definitions along with of_find_backlight_by_node in
linux/backlight.h as I hadn't realized that each .c file should strictly
have a one to one correspondence with the .h file of the same name but
as you mentioned, it is necessary in a large/complex project like this.
Thank you for the clarifications !
Regards,
Meghana
>
> >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.
> >>>>
>
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