Re: [PATCH v2] drm: Add Grain Media GM12U320 kms driver

[Thierry Reding <thierry.reding@gmail.com>]

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On Fri, Jun 03, 2016 at 03:06:32PM +0200, Hans de Goede wrote:
> Grain-media GM12U320 based devices are mini video projectors using USB for
> both power and video data transport.
> 
> This commit adds a kms driver for these devices, including prime support.
> 
> This driver is based on the existing udl kms driver, and the gm12u320
> fb driver by Viacheslav Nurmekhamitov <slavrn@yandex.ru>.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
> Changes in v2:
> -Rebase on 4.7-rc1
> -Sync with udl, bring in any fixes done to udl since v1

This sounds a little nightmarish in the long term. From a cursory look
this duplicates a bunch of code that's present in UDL, where the main
differences are EDID handling and data transfer. I wonder if we can't
find a better way of reusing code than duplicating it.

> diff --git a/drivers/gpu/drm/gm12u320/gm12u320_connector.c b/drivers/gpu/drm/gm12u320/gm12u320_connector.c
[...]
> +/*
> + * Note this assumes this driver is only ever used with the Acer C120, if we
> + * add support for other devices the vendor and model should be parameterized.
> + */
> +static struct edid gm12u320_edid = {
> +	.header		= { 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00 },
> +	.mfg_id		= { 0x04, 0x72 },	/* "ACR" */
> +	.prod_code	= { 0x20, 0xc1 },	/* C120h */
> +	.mfg_week	= 1,
> +	.mfg_year	= 1,
> +	.version	= 1,			/* EDID 1.3 */
> +	.revision	= 3,			/* EDID 1.3 */
> +	.input		= 0x80,			/* Digital input */
> +	.features	= 0x02,			/* Pref timing in DTD 1 */
> +	.standard_timings = { { 1, 1 }, { 1, 1 }, { 1, 1 }, { 1, 1 },
> +			      { 1, 1 }, { 1, 1 }, { 1, 1 }, { 1, 1 } },
> +	.detailed_timings = { {
> +		.pixel_clock = 3383,
> +		/* hactive = 852, hblank = 256 */
> +		.data.pixel_data.hactive_lo = 0x54,
> +		.data.pixel_data.hblank_lo = 0x00,
> +		.data.pixel_data.hactive_hblank_hi = 0x31,
> +		/* vactive = 480, vblank = 28 */
> +		.data.pixel_data.vactive_lo = 0xe0,
> +		.data.pixel_data.vblank_lo = 0x1c,
> +		.data.pixel_data.vactive_vblank_hi = 0x10,
> +		/* hsync offset 40 pw 128, vsync offset 1 pw 4 */
> +		.data.pixel_data.hsync_offset_lo = 0x28,
> +		.data.pixel_data.hsync_pulse_width_lo = 0x80,
> +		.data.pixel_data.vsync_offset_pulse_width_lo = 0x14,
> +		.data.pixel_data.hsync_vsync_offset_pulse_width_hi = 0x00,
> +		/* Digital separate syncs, hsync+, vsync+ */
> +		.data.pixel_data.misc = 0x1e,
> +	}, {
> +		.pixel_clock = 0,
> +		.data.other_data.type = 0xfd, /* Monitor ranges */
> +		.data.other_data.data.range.min_vfreq = 59,
> +		.data.other_data.data.range.max_vfreq = 61,
> +		.data.other_data.data.range.min_hfreq_khz = 29,
> +		.data.other_data.data.range.max_hfreq_khz = 32,
> +		.data.other_data.data.range.pixel_clock_mhz = 4, /* 40 MHz */
> +		.data.other_data.data.range.flags = 0,
> +		.data.other_data.data.range.formula.cvt = {
> +			0xa0, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20 },
> +	}, {
> +		.pixel_clock = 0,
> +		.data.other_data.type = 0xfc, /* Model string */
> +		.data.other_data.data.str.str = {
> +			'C', '1', '2', '0', 'P', 'r', 'o', 'j', 'e', 'c',
> +			't', 'o', 'r' },
> +	}, {
> +		.pixel_clock = 0,
> +		.data.other_data.type = 0xfe, /* Unspecified text / padding */
> +		.data.other_data.data.str.str = {
> +			'\n', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ',
> +			' ', ' ',  ' ' },
> +	} },
> +	.checksum = 0x40,
> +};

Where did you get this from? Doesn't this device have a chip that you
can query at runtime?

> +static int gm12u320_connector_set_property(struct drm_connector *connector,
> +					   struct drm_property *property,
> +					   uint64_t val)
> +{
> +	return 0;
> +}

Just drop it if it doesn't do anything.

> +int gm12u320_connector_init(struct drm_device *dev,
> +			    struct drm_encoder *encoder)
> +{
> +	struct drm_connector *connector;
> +
> +	connector = kzalloc(sizeof(struct drm_connector), GFP_KERNEL);
> +	if (!connector)
> +		return -ENOMEM;
> +
> +	drm_connector_init(dev, connector, &gm12u320_connector_funcs,
> +			   DRM_MODE_CONNECTOR_Unknown);

According to the Grain Media website this chip is a USB 3.0-to-HDMI
bridge, so DRM_MODE_CONNECTOR_HDMIA might be a better choice here.

> diff --git a/drivers/gpu/drm/gm12u320/gm12u320_drv.c b/drivers/gpu/drm/gm12u320/gm12u320_drv.c
[...]
> new file mode 100644
> index 0000000..eff3a44
> --- /dev/null
> +++ b/drivers/gpu/drm/gm12u320/gm12u320_drv.c
> @@ -0,0 +1,160 @@
> +/*
> + * Copyright (C) 2012-2016 Red Hat Inc.
> + *
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License v2. See the file COPYING in the main directory of this archive for
> + * more details.
> + */
> +
> +#include <linux/module.h>
> +#include <drm/drmP.h>
> +#include <drm/drm_crtc_helper.h>
> +#include "gm12u320_drv.h"
> +
> +static int gm12u320_driver_set_busid(struct drm_device *d, struct drm_master *m)
> +{
> +	return 0;
> +}

This is optional, you can drop it.

Thierry

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