Den 29.09.2017 16.13, skrev Meghana Madhyastha:
On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Trønnes wrote:
Den 29.09.2017 14.20, skrev Meghana Madhyastha:
On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
Den 29.09.2017 05.22, skrev Meghana Madhyastha:
On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
Den 28.09.2017 16.08, skrev Daniel Vetter:
On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
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 v3:
-Change it back to a single patch from two patches in v2
drivers/gpu/drm/drm_of.c | 44 ++++++++++++++++++++++++++
drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
drivers/gpu/drm/tinydrm/mi0283qt.c | 3 +-
include/drm/drm_of.h | 1 +
include/drm/tinydrm/tinydrm-helpers.h | 1 -
5 files changed, 47 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);
<snip>
Another problem I discovered when trying to compile this, is that if
DRM is builtin and LCD_CLASS_DEVICE is a module:
drivers/gpu/drm/drm_of.c:292: undefined reference to
`of_find_backlight_by_node'
I see that I solved this in tinydrm by just selecting
BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
Arnd fixed a similar type of dependecy in the repaper driver by forcing
repaper to be a module if necessary. To be honest, I don't know why his
fix works:
https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
I didn't quite understand how we could use this fix for the current
case. Isn't this specific to the repaper driver dependency ?
This is the solution Daniel mentions:
menuconfig DRM
tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
support)"
depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
+ depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
I had tried this but it resulted in a recursive dependencies error.
What's the error?
Could this have something to do with tinydrm selecting backlight and
depending on DRM?
Noralf.
Looks like a case of circular dependencies. The exact error is this:
scripts/kconfig/mconf Kconfig
drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:7: symbol DRM depends on LCD_CLASS_DEVICE
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/backlight/Kconfig:16: symbol LCD_CLASS_DEVICE is
selected by FB_CLPS711X
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/fbdev/Kconfig:338: symbol FB_CLPS711X depends on FB
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/fbdev/Kconfig:5: symbol FB is selected by
DRM_KMS_FB_HELPER
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:73: symbol DRM_KMS_FB_HELPER is selected by
DRM_FBDEV_EMULATION
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:90: symbol DRM_FBDEV_EMULATION depends on
DRM
Long story short, the dependency loop is as follows:
DRM -> LCD_CLASS_DEVICE -> FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
DRM_FBDEV_EMULATION -> DRM
I have messed up the options here, it should be BACKLIGHT_CLASS_DEVICE:
menuconfig DRM
depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
It doesn't help with the recusrsive problem, but at least it makes sense:
drivers/gpu/drm/Kconfig:7: symbol DRM depends on BACKLIGHT_CLASS_DEVICE
drivers/video/backlight/Kconfig:158: symbol BACKLIGHT_CLASS_DEVICE is
selected by DRM_RADEON
drivers/gpu/drm/Kconfig:164: symbol DRM_RADEON depends on DRM
I don't know how to solve this...
Noralf.
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