[PATCH 04/86] drm: Add client-agnostic setup helper

[Thomas Zimmermann]

Hi

Am 18.08.24 um 22:07 schrieb Laurent Pinchart:
> Hi Thomas,
>
> Thank you for the patch.
>
> On Fri, Aug 16, 2024 at 02:22:30PM +0200, Thomas Zimmermann wrote:
>> DRM may support multiple in-kernel clients that run as soon as a DRM
>> driver has been registered. To select the client(s) in a single place,
>> introduce drm_client_setup().
>>
>> Drivers that call the new helper automatically instantiate the kernel's
>> configured default clients. Only fbdev emulation is currently supported.
>> Later versions can add support for DRM-based logging, a boot logo or even
>> a console.
> I really like the direction this is taking :-)
>
>> Some drivers handle the color mode for clients internally. Provide the
>> helper drm_client_setup_with_color_mode() for them.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> ---
>>   drivers/gpu/drm/Makefile           |  1 +
>>   drivers/gpu/drm/drm_client_setup.c | 55 ++++++++++++++++++++++++++++++
>>   include/drm/drm_client_setup.h     | 12 +++++++
>>   3 files changed, 68 insertions(+)
>>   create mode 100644 drivers/gpu/drm/drm_client_setup.c
>>   create mode 100644 include/drm/drm_client_setup.h
>>
>> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
>> index 0beb55d028a8..e7fc77d1d573 100644
>> --- a/drivers/gpu/drm/Makefile
>> +++ b/drivers/gpu/drm/Makefile
>> @@ -129,6 +129,7 @@ drm_kms_helper-y := \
>>   	drm_atomic_helper.o \
>>   	drm_atomic_state_helper.o \
>>   	drm_bridge_connector.o \
>> +	drm_client_setup.o \
>>   	drm_crtc_helper.o \
>>   	drm_damage_helper.o \
>>   	drm_encoder_slave.o \
>> diff --git a/drivers/gpu/drm/drm_client_setup.c b/drivers/gpu/drm/drm_client_setup.c
>> new file mode 100644
>> index 000000000000..2e3315f5c3e2
>> --- /dev/null
>> +++ b/drivers/gpu/drm/drm_client_setup.c
>> @@ -0,0 +1,55 @@
>> +// SPDX-License-Identifier: MIT
>> +
>> +#include <drm/drm_client_setup.h>
>> +#include <drm/drm_device.h>
>> +#include <drm/drm_fbdev_client.h>
>> +#include <drm/drm_fourcc.h>
>> +#include <drm/drm_print.h>
>> +
>> +/**
>> + * drm_client_setup() - Setup in-kernel DRM clients
>> + * @dev: DRM device
>> + * @format: Preferred color format for the device. Use NULL, unless
> s/color format/pixel format/

Ah, ok.

>
>> + *          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)
>> +{
>> +	int ret;
>> +
>> +	if (!format)
>> +		format = drm_format_info(DRM_FORMAT_XRGB8888);
>> +
>> +	ret = drm_fbdev_client_setup(dev, format);
>> +	if (ret)
>> +		drm_warn(dev, "Failed to set up DRM client; error %d\n", ret);
>> +}
>> +EXPORT_SYMBOL(drm_client_setup);
>> +
>> +/**
>> + * 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)
>> +{
>> +	uint32_t fmt = drm_driver_color_mode_format(dev, color_mode);
>> +
>> +	drm_client_setup(dev, drm_format_info(fmt));
>> +}
>> +EXPORT_SYMBOL(drm_client_setup_with_color_mode);
>> diff --git a/include/drm/drm_client_setup.h b/include/drm/drm_client_setup.h
>> new file mode 100644
>> index 000000000000..f5fd1fabd4b1
>> --- /dev/null
>> +++ b/include/drm/drm_client_setup.h
>> @@ -0,0 +1,12 @@
>> +/* SPDX-License-Identifier: MIT */
>> +
>> +#ifndef DRM_CLIENT_SETUP_H
>> +#define DRM_CLIENT_SETUP_H
>> +
>> +struct drm_device;
>> +struct drm_format_info;
>> +
>> +void drm_client_setup(struct drm_device *dev, const struct drm_format_info *format);
>> +void drm_client_setup_with_color_mode(struct drm_device *dev, unsigned int color_mode);
> This is not common in DRM, so we may not want to introduce it here, but
> _Generic() gives a nice function overloading syntax:
>
> void drm_client_setup_with_format(struct drm_device *dev, const struct drm_format_info *format);
> void drm_client_setup_with_color_mode(struct drm_device *dev, unsigned int color_mode);
>
> #define drm_client_setup_(dev, format_or_color_mode)							 \
> 	_Generic(format_or_color_mode,									 \
> 		const struct drm_format_info *: drm_client_setup_with_format(dev, format_or_color_mode), \
> 		unsigned int: drm_client_setup_with_color_mode(dev, format_or_color_mode)		 \
> 	)
>
> Up to you.

The color format is really a user interface. I'd rather like to remove 
it from the implementation where possible.

Best regards
Thomas

>
> Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
>
>> +
>> +#endif

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)