linux/drivers/gpu/drm/clients/drm_client_setup.c
Thierry Reding cce91f29c0 drm/fbdev-client: Skip DRM clients if modesetting is absent
Recent generations of Tegra have moved the display components outside of
host1x, leading to a device that has no CRTCs attached and hence doesn't
support any of the modesetting functionality. When this is detected, the
driver clears the DRIVER_MODESET and DRIVER_ATOMIC flags for the device.

Unfortunately, this causes the following errors during boot:

    [      15.418958] ERR KERN drm drm: [drm] *ERROR* Failed to register client: -95
    [      15.425311] WARNING KERN drm drm: [drm] Failed to set up DRM client; error -95

These originate from the fbdev client checking for the presence of the
DRIVER_MODESET flag and returning -EOPNOTSUPP. However, if a driver does
not support DRIVER_MODESET this is entirely expected and the error isn't
helpful.

Prevent this misleading error message by setting up the DRM clients only
if modesetting is enabled.

Changes in v2:
- use DRIVER_MODESET check to avoid registering any clients

Reported-by: Jonathan Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250613122838.2082334-1-thierry.reding@gmail.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
2025-07-06 14:05:07 +03:00

98 lines
3 KiB
C

// SPDX-License-Identifier: MIT
#include <linux/export.h>
#include <drm/clients/drm_client_setup.h>
#include <drm/drm_device.h>
#include <drm/drm_drv.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_print.h>
#include "drm_client_internal.h"
static char drm_client_default[16] = CONFIG_DRM_CLIENT_DEFAULT;
module_param_string(active, drm_client_default, sizeof(drm_client_default), 0444);
MODULE_PARM_DESC(active,
"Choose which drm client to start, default is"
CONFIG_DRM_CLIENT_DEFAULT "]");
/**
* drm_client_setup() - Setup in-kernel DRM clients
* @dev: DRM device
* @format: Preferred pixel format for the device. Use NULL, unless
* there is clearly a driver-preferred format.
*
* This function sets up the in-kernel DRM clients. Restore, hotplug
* events and teardown are all taken care of.
*
* Drivers should call drm_client_setup() after registering the new
* DRM device with drm_dev_register(). This function is safe to call
* even when there are no connectors present. Setup will be retried
* on the next hotplug event.
*
* The clients are destroyed by drm_dev_unregister().
*/
void drm_client_setup(struct drm_device *dev, const struct drm_format_info *format)
{
if (!drm_core_check_feature(dev, DRIVER_MODESET)) {
drm_dbg(dev, "driver does not support mode-setting, skipping DRM clients\n");
return;
}
#ifdef CONFIG_DRM_FBDEV_EMULATION
if (!strcmp(drm_client_default, "fbdev")) {
int ret;
ret = drm_fbdev_client_setup(dev, format);
if (ret)
drm_warn(dev, "Failed to set up DRM client; error %d\n", ret);
return;
}
#endif
#ifdef CONFIG_DRM_CLIENT_LOG
if (!strcmp(drm_client_default, "log")) {
drm_log_register(dev);
return;
}
#endif
if (strcmp(drm_client_default, ""))
drm_warn(dev, "Unknown DRM client %s\n", drm_client_default);
}
EXPORT_SYMBOL(drm_client_setup);
/**
* drm_client_setup_with_fourcc() - Setup in-kernel DRM clients for color mode
* @dev: DRM device
* @fourcc: Preferred pixel format as 4CC code for the device
*
* This function sets up the in-kernel DRM clients. It is equivalent
* to drm_client_setup(), but expects a 4CC code as second argument.
*/
void drm_client_setup_with_fourcc(struct drm_device *dev, u32 fourcc)
{
drm_client_setup(dev, drm_format_info(fourcc));
}
EXPORT_SYMBOL(drm_client_setup_with_fourcc);
/**
* drm_client_setup_with_color_mode() - Setup in-kernel DRM clients for color mode
* @dev: DRM device
* @color_mode: Preferred color mode for the device
*
* This function sets up the in-kernel DRM clients. It is equivalent
* to drm_client_setup(), but expects a color mode as second argument.
*
* Do not use this function in new drivers. Prefer drm_client_setup() with a
* format of NULL.
*/
void drm_client_setup_with_color_mode(struct drm_device *dev, unsigned int color_mode)
{
u32 fourcc = drm_driver_color_mode_format(dev, color_mode);
drm_client_setup_with_fourcc(dev, fourcc);
}
EXPORT_SYMBOL(drm_client_setup_with_color_mode);
MODULE_DESCRIPTION("In-kernel DRM clients");
MODULE_LICENSE("GPL and additional rights");