Re: [PATCH 1/2] drm/hyperv: Add DRM driver for hyperv synthetic video device

From: Thomas Zimmermann <tzimmermann@suse.de>
To: Deepak Rawat <drawat.floss@gmail.com>,
	linux-hyperv@vger.kernel.org, dri-devel@lists.freedesktop.org
Cc: Daniel Vetter <daniel@ffwll.ch>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Sam Ravnborg <sam@ravnborg.org>, Dexuan Cui <decui@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Wei Hu <weh@microsoft.com>,
	Tang Shaofeng <shaofeng.tang@intel.com>,
	Michael Kelley <mikelley@microsoft.com>
Subject: Re: [PATCH 1/2] drm/hyperv: Add DRM driver for hyperv synthetic video device
Date: Mon, 4 Jan 2021 14:03:36 +0100	[thread overview]
Message-ID: <2b49fcd2-38f7-dae5-2992-721a8bd142a2@suse.de> (raw)
In-Reply-To: <20210102060336.832866-1-drawat.floss@gmail.com>

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Hi,

I've been looking forward to this patchset. :) The code is really nice 
already.

Am 02.01.21 um 07:03 schrieb Deepak Rawat:
> DRM driver for hyperv synthetic video device, based on hyperv_fb
> framebuffer driver. Also added config option "DRM_HYPERV" to enabled
> this driver.

IIRC, this isn't the first iteration. Patches should carry a small 
changelog.

> 
> Signed-off-by: Deepak Rawat <drawat.floss@gmail.com>
> ---
>   drivers/gpu/drm/tiny/Kconfig      |   12 +
>   drivers/gpu/drm/tiny/Makefile     |    1 +
>   drivers/gpu/drm/tiny/hyperv_drm.c | 1066 +++++++++++++++++++++++++++++

This is already quite large for tiny/. I'd split-up this source file 
into a hvperv_drm_proto.c file, a hvperv_drm_modeset.c file and a 
hvperv_drm_drv.c file. Modeset.c would contain section "VRAM blit" up to 
"Framebuffers & mode config". Everything before is _proto.c, everything 
below is _drv.c.

If you do so, we can put them into a separate directory (e.g., hyperv).

>   3 files changed, 1079 insertions(+)
>   create mode 100644 drivers/gpu/drm/tiny/hyperv_drm.c
> 
> diff --git a/drivers/gpu/drm/tiny/Kconfig b/drivers/gpu/drm/tiny/Kconfig
> index 2b6414f0fa75..952f8f29ad25 100644
> --- a/drivers/gpu/drm/tiny/Kconfig
> +++ b/drivers/gpu/drm/tiny/Kconfig
> @@ -28,6 +28,18 @@ config DRM_GM12U320
>   	 This is a KMS driver for projectors which use the GM12U320 chipset
>   	 for video transfer over USB2/3, such as the Acer C120 mini projector.
>   
> +config DRM_HYPERV
> +	tristate "DRM Support for hyperv synthetic video device"
> +	depends on DRM && PCI && MMU && HYPERV
> +	select DRM_KMS_HELPER
> +	select DRM_GEM_SHMEM_HELPER

SHMEM helpers might not be a good choice, because you need this blit 
code, which has a memcpy.

I guess it's easily possible to configure 16 MiB or more for the guest's 
VRAM? If so, I suggest to use VRAM helpers. Guests will be able to 
render into VRAM directly with the driver's memcpy. The driver will do 
page flipping. The bochs driver would be an example.

Hyperv doesn't need buffer sharing with other devices, I guess?

> +	help
> +	 This is a KMS driver for hyperv synthetic video device. Choose this
> +	 option if you would like to enable drm driver for Hyper-V virtual
> +	 machine.
> +
> +	 If M is selected the module will be called hyperv_drm.
> +
>   config TINYDRM_HX8357D
>   	tristate "DRM support for HX8357D display panels"
>   	depends on DRM && SPI
> diff --git a/drivers/gpu/drm/tiny/Makefile b/drivers/gpu/drm/tiny/Makefile
> index 6ae4e9e5a35f..837cb2c2637e 100644
> --- a/drivers/gpu/drm/tiny/Makefile
> +++ b/drivers/gpu/drm/tiny/Makefile
> @@ -2,6 +2,7 @@
>   
>   obj-$(CONFIG_DRM_CIRRUS_QEMU)		+= cirrus.o
>   obj-$(CONFIG_DRM_GM12U320)		+= gm12u320.o
> +obj-$(CONFIG_DRM_HYPERV)		+= hyperv_drm.o
>   obj-$(CONFIG_TINYDRM_HX8357D)		+= hx8357d.o
>   obj-$(CONFIG_TINYDRM_ILI9225)		+= ili9225.o
>   obj-$(CONFIG_TINYDRM_ILI9341)		+= ili9341.o
> diff --git a/drivers/gpu/drm/tiny/hyperv_drm.c b/drivers/gpu/drm/tiny/hyperv_drm.c
> new file mode 100644
> index 000000000000..e367df45225a
> --- /dev/null
> +++ b/drivers/gpu/drm/tiny/hyperv_drm.c
> @@ -0,0 +1,1066 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2012-2020 Microsoft
> + *
> + * Authors:
> + * Deepak Rawat <drawat.floss@gmail.com>
> + *
> + * Portions of this code is derived from hyperv_fb.c
> + * drivers/video/fbdev/hyperv_fb.c - framebuffer driver for hyperv synthetic
> + * video device.
> + *
> + */
> +
> +#include <linux/console.h>
> +#include <linux/efi.h>
> +#include <linux/hyperv.h>
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +
> +#include <drm/drm_damage_helper.h>
> +#include <drm/drm_drv.h>
> +#include <drm/drm_fb_helper.h>
> +#include <drm/drm_format_helper.h>
> +#include <drm/drm_gem_shmem_helper.h>
> +#include <drm/drm_gem_framebuffer_helper.h>
> +#include <drm/drm_probe_helper.h>
> +#include <drm/drm_simple_kms_helper.h>
> +
> +#define DRIVER_NAME "hyperv_drm"
> +#define DRIVER_DESC "DRM driver for hyperv synthetic video device"
> +#define DRIVER_DATE "2020"
> +#define DRIVER_MAJOR 1
> +#define DRIVER_MINOR 0
> +
> +#define VMBUS_MAX_PACKET_SIZE 0x4000
> +#define VMBUS_RING_BUFSIZE (256 * 1024)
> +#define VMBUS_VSP_TIMEOUT (10 * HZ)
> +
> +#define PCI_VENDOR_ID_MICROSOFT 0x1414
> +#define PCI_DEVICE_ID_HYPERV_VIDEO 0x5353
> +
> +struct hyperv_device {

Could this name lead to conflicts with other hyperv drivers? I suggest 
to name it hyperv_drm_device.

> +	/* drm */
> +	struct drm_device dev;
> +	struct drm_simple_display_pipe pipe;
> +	struct drm_connector connector;
> +
> +	/* mode */
> +	u32 screen_width_max;
> +	u32 screen_height_max;
> +	u32 preferred_width;
> +	u32 preferred_height;
> +	u32 screen_depth;
> +
> +	/* hw */
> +	struct resource *mem;
> +	void __iomem *vram;
> +	unsigned long fb_base;
> +	unsigned long fb_size;
> +	struct completion wait;
> +	u32 synthvid_version;
> +	u32 mmio_megabytes;
> +
> +	u8 init_buf[VMBUS_MAX_PACKET_SIZE];
> +	u8 recv_buf[VMBUS_MAX_PACKET_SIZE];
> +
> +	struct hv_device *hdev;
> +};
> +
> +#define to_hv(_dev) container_of(_dev, struct hyperv_device, dev)
> +
> +/*
> + * Hyper-V Synthetic Video Protocol
> + */
> +
> +#define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
> +#define SYNTHVID_VER_GET_MAJOR(ver) (ver & 0x0000ffff)
> +#define SYNTHVID_VER_GET_MINOR(ver) ((ver & 0xffff0000) >> 16)
> +#define SYNTHVID_VERSION_WIN7 SYNTHVID_VERSION(3, 0)
> +#define SYNTHVID_VERSION_WIN8 SYNTHVID_VERSION(3, 2)
> +#define SYNTHVID_VERSION_WIN10 SYNTHVID_VERSION(3, 5)
> +
> +#define SYNTHVID_DEPTH_WIN7 16
> +#define SYNTHVID_DEPTH_WIN8 32
> +#define SYNTHVID_FB_SIZE_WIN7 (4 * 1024 * 1024)
> +#define SYNTHVID_FB_SIZE_WIN8 (8 * 1024 * 1024)
> +#define SYNTHVID_WIDTH_MAX_WIN7 1600
> +#define SYNTHVID_HEIGHT_MAX_WIN7 1200
> +
> +enum pipe_msg_type {
> +	PIPE_MSG_INVALID,
> +	PIPE_MSG_DATA,
> +	PIPE_MSG_MAX
> +};
> +
> +enum synthvid_msg_type {
> +	SYNTHVID_ERROR			= 0,
> +	SYNTHVID_VERSION_REQUEST	= 1,
> +	SYNTHVID_VERSION_RESPONSE	= 2,
> +	SYNTHVID_VRAM_LOCATION		= 3,
> +	SYNTHVID_VRAM_LOCATION_ACK	= 4,
> +	SYNTHVID_SITUATION_UPDATE	= 5,
> +	SYNTHVID_SITUATION_UPDATE_ACK	= 6,
> +	SYNTHVID_POINTER_POSITION	= 7,
> +	SYNTHVID_POINTER_SHAPE		= 8,
> +	SYNTHVID_FEATURE_CHANGE		= 9,
> +	SYNTHVID_DIRT			= 10,
> +	SYNTHVID_RESOLUTION_REQUEST	= 13,
> +	SYNTHVID_RESOLUTION_RESPONSE	= 14,
> +
> +	SYNTHVID_MAX			= 15
> +};
> +
> +struct pipe_msg_hdr {
> +	u32 type;
> +	u32 size; /* size of message after this field */
> +} __packed;
> +
> +struct hvd_screen_info {
> +	u16 width;
> +	u16 height;
> +} __packed;
> +
> +struct synthvid_msg_hdr {
> +	u32 type;
> +	u32 size;  /* size of this header + payload after this field */
> +} __packed;
> +
> +struct synthvid_version_req {
> +	u32 version;
> +} __packed;
> +
> +struct synthvid_version_resp {
> +	u32 version;
> +	u8 is_accepted;
> +	u8 max_video_outputs;
> +} __packed;
> +
> +struct synthvid_vram_location {
> +	u64 user_ctx;
> +	u8 is_vram_gpa_specified;
> +	u64 vram_gpa;
> +} __packed;
> +
> +struct synthvid_vram_location_ack {
> +	u64 user_ctx;
> +} __packed;
> +
> +struct video_output_situation {
> +	u8 active;
> +	u32 vram_offset;
> +	u8 depth_bits;
> +	u32 width_pixels;
> +	u32 height_pixels;
> +	u32 pitch_bytes;
> +} __packed;
> +
> +struct synthvid_situation_update {
> +	u64 user_ctx;
> +	u8 video_output_count;
> +	struct video_output_situation video_output[1];
> +} __packed;
> +
> +struct synthvid_situation_update_ack {
> +	u64 user_ctx;
> +} __packed;
> +
> +struct synthvid_pointer_position {
> +	u8 is_visible;
> +	u8 video_output;
> +	s32 image_x;
> +	s32 image_y;
> +} __packed;
> +
> +#define SYNTHVID_CURSOR_MAX_X 96
> +#define SYNTHVID_CURSOR_MAX_Y 96
> +#define SYNTHVID_CURSOR_ARGB_PIXEL_SIZE 4
> +#define SYNTHVID_CURSOR_MAX_SIZE (SYNTHVID_CURSOR_MAX_X * \
> +	SYNTHVID_CURSOR_MAX_Y * SYNTHVID_CURSOR_ARGB_PIXEL_SIZE)
> +#define SYNTHVID_CURSOR_COMPLETE (-1)
> +
> +struct synthvid_pointer_shape {

Do you have plans for adding cursor support?

> +	u8 part_idx;
> +	u8 is_argb;
> +	u32 width; /* SYNTHVID_CURSOR_MAX_X at most */
> +	u32 height; /* SYNTHVID_CURSOR_MAX_Y at most */
> +	u32 hot_x; /* hotspot relative to upper-left of pointer image */
> +	u32 hot_y;
> +	u8 data[4];
> +} __packed;
> +
> +struct synthvid_feature_change {
> +	u8 is_dirt_needed;
> +	u8 is_ptr_pos_needed;
> +	u8 is_ptr_shape_needed;
> +	u8 is_situ_needed;
> +} __packed;
> +
> +struct rect {
> +	s32 x1, y1; /* top left corner */
> +	s32 x2, y2; /* bottom right corner, exclusive */
> +} __packed;
> +
> +struct synthvid_dirt {
> +	u8 video_output;
> +	u8 dirt_count;
> +	struct rect rect[1];
> +} __packed;
> +
> +#define SYNTHVID_EDID_BLOCK_SIZE	128
> +#define	SYNTHVID_MAX_RESOLUTION_COUNT	64
> +
> +struct synthvid_supported_resolution_req {
> +	u8 maximum_resolution_count;
> +} __packed;
> +
> +struct synthvid_supported_resolution_resp {
> +	u8 edid_block[SYNTHVID_EDID_BLOCK_SIZE];
> +	u8 resolution_count;
> +	u8 default_resolution_index;
> +	u8 is_standard;
> +	struct hvd_screen_info supported_resolution[SYNTHVID_MAX_RESOLUTION_COUNT];
> +} __packed;
> +
> +struct synthvid_msg {
> +	struct pipe_msg_hdr pipe_hdr;
> +	struct synthvid_msg_hdr vid_hdr;
> +	union {
> +		struct synthvid_version_req ver_req;
> +		struct synthvid_version_resp ver_resp;
> +		struct synthvid_vram_location vram;
> +		struct synthvid_vram_location_ack vram_ack;
> +		struct synthvid_situation_update situ;
> +		struct synthvid_situation_update_ack situ_ack;
> +		struct synthvid_pointer_position ptr_pos;
> +		struct synthvid_pointer_shape ptr_shape;
> +		struct synthvid_feature_change feature_chg;
> +		struct synthvid_dirt dirt;
> +		struct synthvid_supported_resolution_req resolution_req;
> +		struct synthvid_supported_resolution_resp resolution_resp;
> +	};
> +} __packed;
> +
> +static inline bool synthvid_ver_ge(u32 ver1, u32 ver2)
> +{
> +	if (SYNTHVID_VER_GET_MAJOR(ver1) > SYNTHVID_VER_GET_MAJOR(ver2) ||
> +	    (SYNTHVID_VER_GET_MAJOR(ver1) == SYNTHVID_VER_GET_MAJOR(ver2) &&
> +	     SYNTHVID_VER_GET_MINOR(ver1) >= SYNTHVID_VER_GET_MINOR(ver2)))
> +		return true;
> +
> +	return false;
> +}
> +
> +static inline int synthvid_send(struct hv_device *hdev,
> +				struct synthvid_msg *msg)
> +{
> +	static atomic64_t request_id = ATOMIC64_INIT(0);
> +	struct hyperv_device *hv = hv_get_drvdata(hdev);
> +	int ret;
> +
> +	msg->pipe_hdr.type = PIPE_MSG_DATA;
> +	msg->pipe_hdr.size = msg->vid_hdr.size;
> +
> +	ret = vmbus_sendpacket(hdev->channel, msg,
> +			       msg->vid_hdr.size + sizeof(struct pipe_msg_hdr),
> +			       atomic64_inc_return(&request_id),
> +			       VM_PKT_DATA_INBAND, 0);
> +
> +	if (ret)
> +		drm_err(&hv->dev, "Unable to send packet via vmbus\n");
> +
> +	return ret;
> +}
> +
> +static int synthvid_negotiate_ver(struct hv_device *hdev, u32 ver)
> +{
> +	struct hyperv_device *hv = hv_get_drvdata(hdev);
> +	struct synthvid_msg *msg = (struct synthvid_msg *)hv->init_buf;
> +	struct drm_device *dev = &hv->dev;
> +	unsigned long t;
> +	int ret = 0;
> +
> +	memset(msg, 0, sizeof(struct synthvid_msg));
> +	msg->vid_hdr.type = SYNTHVID_VERSION_REQUEST;
> +	msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
> +		sizeof(struct synthvid_version_req);
> +	msg->ver_req.version = ver;
> +	synthvid_send(hdev, msg);
> +
> +	t = wait_for_completion_timeout(&hv->wait, VMBUS_VSP_TIMEOUT);
> +	if (!t) {
> +		drm_err(dev, "Time out on waiting version response\n");
> +		ret = -ETIMEDOUT;
> +		goto out;
> +	}
> +	if (!msg->ver_resp.is_accepted) {
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	hv->synthvid_version = ver;
> +	drm_info(dev, "Synthvid Version major %d, minor %d\n",
> +		 SYNTHVID_VER_GET_MAJOR(ver), SYNTHVID_VER_GET_MINOR(ver));
> +
> +out:
> +	return ret;
> +}
> +
> +static int synthvid_update_vram_location(struct hv_device *hdev,
> +					 phys_addr_t vram_pp)
> +{
> +	struct hyperv_device *hv = hv_get_drvdata(hdev);
> +	struct synthvid_msg *msg = (struct synthvid_msg *)hv->init_buf;
> +	struct drm_device *dev = &hv->dev;
> +	unsigned long t;
> +	int ret = 0;
> +
> +	memset(msg, 0, sizeof(struct synthvid_msg));
> +	msg->vid_hdr.type = SYNTHVID_VRAM_LOCATION;
> +	msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
> +		sizeof(struct synthvid_vram_location);
> +	msg->vram.user_ctx = vram_pp;
> +	msg->vram.vram_gpa = vram_pp;
> +	msg->vram.is_vram_gpa_specified = 1;
> +	synthvid_send(hdev, msg);
> +
> +	t = wait_for_completion_timeout(&hv->wait, VMBUS_VSP_TIMEOUT);
> +	if (!t) {
> +		drm_err(dev, "Time out on waiting vram location ack\n");
> +		ret = -ETIMEDOUT;
> +		goto out;
> +	}
> +	if (msg->vram_ack.user_ctx != vram_pp) {
> +		drm_err(dev, "Unable to set VRAM location\n");
> +		ret = -ENODEV;
> +	}
> +
> +out:
> +	return ret;
> +}
> +
> +static int synthvid_update_situation(struct hv_device *hdev, u8 active, u32 bpp,
> +				     u32 w, u32 h, u32 pitch)
> +{
> +	struct synthvid_msg msg;
> +
> +	memset(&msg, 0, sizeof(struct synthvid_msg));
> +
> +	msg.vid_hdr.type = SYNTHVID_SITUATION_UPDATE;
> +	msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
> +		sizeof(struct synthvid_situation_update);
> +	msg.situ.user_ctx = 0;
> +	msg.situ.video_output_count = 1;
> +	msg.situ.video_output[0].active = active;
> +	/* vram_offset should always be 0 */
> +	msg.situ.video_output[0].vram_offset = 0;
> +	msg.situ.video_output[0].depth_bits = bpp;
> +	msg.situ.video_output[0].width_pixels = w;
> +	msg.situ.video_output[0].height_pixels = h;
> +	msg.situ.video_output[0].pitch_bytes = pitch;
> +
> +	synthvid_send(hdev, &msg);
> +
> +	return 0;
> +}
> +
> +static int synthvid_update_dirt(struct hv_device *hdev, struct drm_rect *rect)
> +{
> +	struct synthvid_msg msg;
> +
> +	memset(&msg, 0, sizeof(struct synthvid_msg));
> +
> +	msg.vid_hdr.type = SYNTHVID_DIRT;
> +	msg.vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
> +		sizeof(struct synthvid_dirt);
> +	msg.dirt.video_output = 0;
> +	msg.dirt.dirt_count = 1;
> +	msg.dirt.rect[0].x1 = rect->x1;
> +	msg.dirt.rect[0].y1 = rect->y1;
> +	msg.dirt.rect[0].x2 = rect->x2;
> +	msg.dirt.rect[0].y2 = rect->y2;
> +
> +	synthvid_send(hdev, &msg);
> +
> +	return 0;
> +}
> +
> +static int synthvid_get_supported_resolution(struct hv_device *hdev)
> +{
> +	struct hyperv_device *hv = hv_get_drvdata(hdev);
> +	struct synthvid_msg *msg = (struct synthvid_msg *)hv->init_buf;
> +	struct drm_device *dev = &hv->dev;
> +	unsigned long t;
> +	int ret = 0;
> +	u8 index;
> +	int i;
> +
> +	memset(msg, 0, sizeof(struct synthvid_msg));
> +	msg->vid_hdr.type = SYNTHVID_RESOLUTION_REQUEST;
> +	msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) +
> +		sizeof(struct synthvid_supported_resolution_req);
> +	msg->resolution_req.maximum_resolution_count =
> +		SYNTHVID_MAX_RESOLUTION_COUNT;
> +	synthvid_send(hdev, msg);
> +
> +	t = wait_for_completion_timeout(&hv->wait, VMBUS_VSP_TIMEOUT);
> +	if (!t) {
> +		drm_err(dev, "Time out on waiting resolution response\n");
> +		ret = -ETIMEDOUT;
> +		goto out;
> +	}
> +
> +	if (msg->resolution_resp.resolution_count == 0) {
> +		drm_err(dev, "No supported resolutions\n");
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	index = msg->resolution_resp.default_resolution_index;
> +	if (index >= msg->resolution_resp.resolution_count) {
> +		drm_err(dev, "Invalid resolution index: %d\n", index);
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +
> +	for (i = 0; i < msg->resolution_resp.resolution_count; i++) {
> +		hv->screen_width_max = max_t(u32, hv->screen_width_max,
> +			msg->resolution_resp.supported_resolution[i].width);
> +		hv->screen_height_max = max_t(u32, hv->screen_height_max,
> +			msg->resolution_resp.supported_resolution[i].height);
> +	}
> +
> +	hv->preferred_width =
> +		msg->resolution_resp.supported_resolution[index].width;
> +	hv->preferred_height =
> +		msg->resolution_resp.supported_resolution[index].height;
> +
> +out:
> +	return ret;
> +}
> +
> +static void synthvid_recv_sub(struct hv_device *hdev)
> +{
> +	struct hyperv_device *hv = hv_get_drvdata(hdev);
> +	struct synthvid_msg *msg;
> +
> +	if (!hv)
> +		return;
> +
> +	msg = (struct synthvid_msg *)hv->recv_buf;
> +
> +	/* Complete the wait event */
> +	if (msg->vid_hdr.type == SYNTHVID_VERSION_RESPONSE ||
> +	    msg->vid_hdr.type == SYNTHVID_RESOLUTION_RESPONSE ||
> +	    msg->vid_hdr.type == SYNTHVID_VRAM_LOCATION_ACK) {
> +		memcpy(hv->init_buf, msg, VMBUS_MAX_PACKET_SIZE);
> +		complete(&hv->wait);
> +		return;
> +	}
> +}
> +
> +static void synthvid_receive(void *ctx)
> +{
> +	struct hv_device *hdev = ctx;
> +	struct hyperv_device *hv = hv_get_drvdata(hdev);
> +	struct synthvid_msg *recv_buf;
> +	u32 bytes_recvd;
> +	u64 req_id;
> +	int ret;
> +
> +	if (!hv)
> +		return;
> +
> +	recv_buf = (struct synthvid_msg *)hv->recv_buf;
> +
> +	do {
> +		ret = vmbus_recvpacket(hdev->channel, recv_buf,
> +				       VMBUS_MAX_PACKET_SIZE,
> +				       &bytes_recvd, &req_id);
> +		if (bytes_recvd > 0 &&
> +		    recv_buf->pipe_hdr.type == PIPE_MSG_DATA)
> +			synthvid_recv_sub(hdev);
> +	} while (bytes_recvd > 0 && ret == 0);
> +}
> +
> +static int synthvid_connect_vsp(struct hv_device *hdev)
> +{
> +	struct hyperv_device *hv = hv_get_drvdata(hdev);
> +	struct drm_device *dev = &hv->dev;
> +	int ret;
> +
> +	ret = vmbus_open(hdev->channel, VMBUS_RING_BUFSIZE, VMBUS_RING_BUFSIZE,
> +			 NULL, 0, synthvid_receive, hdev);
> +	if (ret) {
> +		drm_err(dev, "Unable to open vmbus channel\n");
> +		return ret;
> +	}
> +
> +	/* Negotiate the protocol version with host */
> +	switch (vmbus_proto_version) {
> +	case VERSION_WIN10:
> +	case VERSION_WIN10_V5:
> +		ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN10);
> +		if (!ret)
> +			break;
> +		fallthrough;
> +	case VERSION_WIN8:
> +	case VERSION_WIN8_1:
> +		ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN8);
> +		if (!ret)
> +			break;
> +		fallthrough;
> +	case VERSION_WS2008:
> +	case VERSION_WIN7:
> +		ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN7);
> +		break;
> +	default:
> +		ret = synthvid_negotiate_ver(hdev, SYNTHVID_VERSION_WIN10);

I don't get the logic of this switch statement. If the host is Win10, 
I'd expect the graphics device to use Win10's protocol, if the host is 
Win8, the graphics device uses win8 protocols. So what's the point of 
the fallthroughs? Can there be newer versions of vmbus_proto_version 
that only support older devices?

> +		break;
> +	}
> +
> +	if (ret) {
> +		drm_err(dev, "Synthetic video device version not accepted %d\n",
> +			ret);
> +		goto error;
> +	}
> +
> +	if (hv->synthvid_version == SYNTHVID_VERSION_WIN7)
> +		hv->screen_depth = SYNTHVID_DEPTH_WIN7;
> +	else
> +		hv->screen_depth = SYNTHVID_DEPTH_WIN8;
> +
> +	if (synthvid_ver_ge(hv->synthvid_version, SYNTHVID_VERSION_WIN10)) {
> +		ret = synthvid_get_supported_resolution(hdev);
> +		if (ret)
> +			drm_err(dev, "Failed to get supported resolution from host, use default\n");
> +	} else {
> +		hv->screen_width_max = SYNTHVID_WIDTH_MAX_WIN7;
> +		hv->screen_height_max = SYNTHVID_HEIGHT_MAX_WIN7;
> +	}
> +
> +	hv->mmio_megabytes = hdev->channel->offermsg.offer.mmio_megabytes;
> +
> +	return 0;
> +
> +error:
> +	vmbus_close(hdev->channel);
> +	return ret;
> +}
> +
> +/*
> + * VRAM blit
> + */
> +
> +static int hyperv_blit_to_vram_rect(struct drm_framebuffer *fb,
> +				    struct drm_rect *rect)
> +{
> +	struct hyperv_device *hv = to_hv(fb->dev);
> +	struct dma_buf_map map;
> +	void *vmap;
> +	int idx, ret;
> +
> +	if (!drm_dev_enter(&hv->dev, &idx))
> +		return -ENODEV;
> +
> +	ret = drm_gem_shmem_vmap(fb->obj[0], &map);
> +	if (ret) {
> +		drm_dev_exit(idx);
> +		return ret;
> +	}
> +
> +	vmap = map.vaddr;
> +	drm_fb_memcpy_dstclip(hv->vram, vmap, fb, rect);
> +	drm_gem_shmem_vunmap(fb->obj[0], vmap);
> +	drm_dev_exit(idx);
> +
> +	return 0;
> +}
> +
> +static int hyperv_blit_to_vram_fullscreen(struct drm_framebuffer *fb)
> +{
> +	struct drm_rect fullscreen = {
> +		.x1 = 0,
> +		.x2 = fb->width,
> +		.y1 = 0,
> +		.y2 = fb->height,
> +	};
> +	return hyperv_blit_to_vram_rect(fb, &fullscreen);
> +}
> +
> +/*
> + * Connector
> + */
> +
> +static int hyperv_connector_get_modes(struct drm_connector *connector)
> +{
> +	struct hyperv_device *hv = to_hv(connector->dev);
> +	int count;
> +
> +	count = drm_add_modes_noedid(connector,
> +				     connector->dev->mode_config.max_width,
> +				     connector->dev->mode_config.max_height);
> +	drm_set_preferred_mode(connector, hv->preferred_width,
> +			       hv->preferred_height);
> +
> +	return count;
> +}
> +
> +static const struct drm_connector_helper_funcs hyperv_connector_helper_funcs = {
> +	.get_modes = hyperv_connector_get_modes,
> +};
> +
> +static const struct drm_connector_funcs hyperv_connector_funcs = {
> +	.fill_modes = drm_helper_probe_single_connector_modes,
> +	.destroy = drm_connector_cleanup,
> +	.reset = drm_atomic_helper_connector_reset,
> +	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> +	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> +};
> +
> +static int hyperv_conn_init(struct hyperv_device *hv)
> +{
> +	drm_connector_helper_add(&hv->connector, &hyperv_connector_helper_funcs);
> +	return drm_connector_init(&hv->dev, &hv->connector,
> +				  &hyperv_connector_funcs,
> +				  DRM_MODE_CONNECTOR_VGA);
> +}
> +
> +/*
> + * Display pipe
> + */
> +
> +static int hyperv_check_size(struct hyperv_device *hv, int w, int h,
> +			     struct drm_framebuffer *fb)
> +{
> +	u32 pitch = w * (hv->screen_depth / 8);
> +
> +	if (fb)
> +		pitch = fb->pitches[0];
> +
> +	if (pitch * h > hv->fb_size)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static enum drm_mode_status
> +hyperv_pipe_mode_valid(struct drm_simple_display_pipe *pipe,
> +		       const struct drm_display_mode *mode)
> +{
> +	struct hyperv_device *hv = to_hv(pipe->crtc.dev);
> +
> +	if (hyperv_check_size(hv, mode->hdisplay, mode->vdisplay, NULL))
> +		return MODE_BAD;
> +
> +	return MODE_OK;
> +}

It's not wrong, but you may rather implement 
drm_mode_config_funcs.mode_valid with this code. VRAM size is a 
device-wide constrait and better fits there.

> +
> +static void hyperv_pipe_enable(struct drm_simple_display_pipe *pipe,
> +			       struct drm_crtc_state *crtc_state,
> +			       struct drm_plane_state *plane_state)
> +{
> +	struct hyperv_device *hv = to_hv(pipe->crtc.dev);
> +
> +	synthvid_update_situation(hv->hdev, 1,  hv->screen_depth,
> +				  crtc_state->mode.hdisplay,
> +				  crtc_state->mode.vdisplay,
> +				  plane_state->fb->pitches[0]);
> +	hyperv_blit_to_vram_fullscreen(plane_state->fb);
> +}
> +
> +static void hyperv_pipe_update(struct drm_simple_display_pipe *pipe,
> +			       struct drm_plane_state *old_state)
> +{
> +	struct hyperv_device *hv = to_hv(pipe->crtc.dev);
> +	struct drm_plane_state *state = pipe->plane.state;
> +	struct drm_rect rect;
> +
> +	if (drm_atomic_helper_damage_merged(old_state, state, &rect)) {
> +		hyperv_blit_to_vram_rect(state->fb, &rect);
> +		synthvid_update_dirt(hv->hdev, &rect);
> +	}
> +}
> +
> +static const struct drm_simple_display_pipe_funcs hyperv_pipe_funcs = {
> +	.mode_valid = hyperv_pipe_mode_valid,
> +	.enable	= hyperv_pipe_enable,
> +	.update	= hyperv_pipe_update,
> +};
> +
> +static const uint32_t hyperv_formats[] = {
> +	DRM_FORMAT_XRGB8888,
> +};
> +
> +static const uint64_t hyperv_modifiers[] = {
> +	DRM_FORMAT_MOD_LINEAR,
> +	DRM_FORMAT_MOD_INVALID
> +};
> +
> +static int hyperv_pipe_init(struct hyperv_device *hv)
> +{
> +	int ret;
> +
> +	ret = drm_simple_display_pipe_init(&hv->dev,
> +					   &hv->pipe,
> +					   &hyperv_pipe_funcs,
> +					   hyperv_formats,
> +					   ARRAY_SIZE(hyperv_formats),
> +					   NULL,
> +					   &hv->connector);
> +
> +	drm_plane_enable_fb_damage_clips(&hv->pipe.plane);
> +
> +	return ret;
> +}
> +
> +/*
> + * Framebuffers & mode config
> + */
> +
> +static struct drm_framebuffer*
> +hyperv_fb_create(struct drm_device *dev, struct drm_file *file_priv,
> +		 const struct drm_mode_fb_cmd2 *mode_cmd)
> +{
> +	struct hyperv_device *hv = to_hv(dev);
> +
> +	if (mode_cmd->pixel_format != DRM_FORMAT_XRGB8888)
> +		return ERR_PTR(-EINVAL);
> +
> +	if (mode_cmd->pitches[0] * mode_cmd->height > hv->fb_size)
> +		return ERR_PTR(-EINVAL);

These tests check if the FB is usable by the display pipeline. So they 
rather belong into the drm_simple_display_pipe_funcs.check function.

> +
> +	return drm_gem_fb_create_with_dirty(dev, file_priv, mode_cmd);
> +}
> +
> +static const struct drm_mode_config_funcs hyperv_mode_config_funcs = {
> +	.fb_create = hyperv_fb_create,
> +	.atomic_check = drm_atomic_helper_check,
> +	.atomic_commit = drm_atomic_helper_commit,
> +};
> +
> +static int hyperv_mode_config_init(struct hyperv_device *hv)
> +{
> +	struct drm_device *dev = &hv->dev;
> +	int ret;
> +
> +	ret = drmm_mode_config_init(dev);
> +	if (ret) {
> +		drm_err(dev, "Failed to initialized mode setting.\n");
> +		return ret;
> +	}
> +
> +	dev->mode_config.min_width = 0;
> +	dev->mode_config.min_height = 0;
> +	dev->mode_config.max_width = hv->screen_width_max;
> +	dev->mode_config.max_height = hv->screen_height_max;
> +
> +	dev->mode_config.preferred_depth = hv->screen_depth;
> +	dev->mode_config.prefer_shadow = 0;
> +
> +	dev->mode_config.funcs = &hyperv_mode_config_funcs;
> +
> +	ret = hyperv_conn_init(hv);
> +	if (ret) {
> +		drm_err(dev, "Failed to initialized connector.\n");
> +		return ret;
> +	}
> +
> +	ret = hyperv_pipe_init(hv);
> +	if (ret) {
> +		drm_err(dev, "Failed to initialized pipe.\n");
> +		return ret;
> +	}
> +
> +	drm_mode_config_reset(dev);
> +
> +	return 0;
> +}
> +
> +/*
> + * DRM
> + */
> +
> +DEFINE_DRM_GEM_FOPS(hv_fops);
> +
> +static struct drm_driver hyperv_driver = {
> +	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC,
> +
> +	.name		 = DRIVER_NAME,
> +	.desc		 = DRIVER_DESC,
> +	.date		 = DRIVER_DATE,
> +	.major		 = DRIVER_MAJOR,
> +	.minor		 = DRIVER_MINOR,
> +
> +	.fops		 = &hv_fops,
> +	DRM_GEM_SHMEM_DRIVER_OPS,
> +};
> +
> +/*
> + * PCI/vmbus interface
> + */
> +
> +static int hyperv_pci_probe(struct pci_dev *pdev,
> +			    const struct pci_device_id *ent)
> +{
> +	return 0;
> +}
> +
> +static void hyperv_pci_remove(struct pci_dev *pdev)
> +{
> +}
> +
> +static const struct pci_device_id hyperv_pci_tbl[] = {
> +	{
> +		.vendor = PCI_VENDOR_ID_MICROSOFT,
> +		.device = PCI_DEVICE_ID_HYPERV_VIDEO,
> +	},
> +	{ /* end of list */ }
> +};
> +
> +static struct pci_driver hyperv_pci_driver = {
> +	.name =		KBUILD_MODNAME,
> +	.id_table =	hyperv_pci_tbl,
> +	.probe =	hyperv_pci_probe,
> +	.remove =	hyperv_pci_remove,
> +};
> +
> +static int hyperv_get_vram_gen1(struct hyperv_device *hv)
> +{
> +	struct drm_device *dev = &hv->dev;
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	pdev = pci_get_device(PCI_VENDOR_ID_MICROSOFT,
> +			      PCI_DEVICE_ID_HYPERV_VIDEO, NULL);
> +	if (!pdev) {
> +		drm_err(dev, "Unable to find PCI Hyper-V video\n");
> +		return -ENODEV;
> +	}
> +
> +	ret = drm_fb_helper_remove_conflicting_pci_framebuffers(pdev, "hypervdrmfb");
> +	if (ret) {
> +		drm_err(dev, "Not able to remove boot fb\n");
> +		return ret;
> +	}
> +
> +	if (pci_request_region(pdev, 0, DRIVER_NAME) != 0)
> +		drm_warn(dev, "Cannot request framebuffer, boot fb still active?\n");
> +
> +	if ((pdev->resource[0].flags & IORESOURCE_MEM) == 0) {
> +		drm_err(dev, "Resource at bar 0 is not IORESOURCE_MEM\n");
> +		ret = -ENODEV;
> +		goto error;
> +	}
> +
> +	hv->fb_base = pci_resource_start(pdev, 0);
> +	hv->fb_size = pci_resource_len(pdev, 0);
> +	if (hv->fb_base == 0) {
> +		drm_err(dev, "Resource not available\n");
> +		ret = -ENODEV;
> +		goto error;
> +	}
> +
> +	hv->fb_size = min(hv->fb_size,
> +			  (unsigned long)(hv->mmio_megabytes * 1024 * 1024));
> +	hv->vram = devm_ioremap(&pdev->dev, hv->fb_base, hv->fb_size);
> +	if (!hv->vram) {
> +		drm_err(dev, "Failed to map vram\n");
> +		ret = -ENOMEM;
> +	}
> +
> +error:
> +	pci_dev_put(pdev);
> +	return ret;
> +}
> +
> +static int hyperv_get_vram_gen2(struct hyperv_device *hv,
> +				struct hv_device *hdev)
> +{
> +	struct drm_device *dev = &hv->dev;
> +	struct apertures_struct *ap;
> +	int ret;
> +
> +	hv->fb_size = (unsigned long)(hv->mmio_megabytes * 1024 * 1024);
> +
> +	ret = vmbus_allocate_mmio(&hv->mem, hdev, 0, -1, hv->fb_size, 0x100000,
> +				  true);
> +	if (ret) {
> +		drm_err(dev, "Failed to allocate mmio\n");
> +		return -ENOMEM;
> +	}
> +
> +	hv->vram = ioremap(hv->mem->start, hv->fb_size);
> +	if (!hv->vram) {
> +		drm_err(dev, "Failed to map vram\n");
> +		ret = -ENOMEM;
> +		goto error;
> +	}
> +
> +	hv->fb_base = hv->mem->start;
> +
> +	ap = alloc_apertures(1);
> +	if (!ap) {
> +		drm_err(dev, "Failed to get apertures\n");
> +		ret = -ENOMEM;
> +		goto error;
> +	}
> +
> +	ap->ranges[0].base = screen_info.lfb_base;
> +	ap->ranges[0].size = screen_info.lfb_size;
> +	remove_conflicting_framebuffers(ap, KBUILD_MODNAME, false);
> +	kfree(ap);
> +
> +	return 0;
> +
> +error:
> +	vmbus_free_mmio(hv->mem->start, hv->fb_size);
> +	return ret;
> +}
> +
> +static int hyperv_vmbus_probe(struct hv_device *hdev,
> +			      const struct hv_vmbus_device_id *dev_id)
> +{
> +	struct hyperv_device *hv;
> +	struct drm_device *dev;
> +	int ret;
> +
> +	hv = devm_drm_dev_alloc(&hdev->device, &hyperv_driver,
> +				struct hyperv_device, dev);
> +	if (IS_ERR(hv))
> +		return PTR_ERR(hv);
> +
> +	dev = &hv->dev;
> +	init_completion(&hv->wait);
> +	hv_set_drvdata(hdev, hv);
> +	hv->hdev = hdev;
> +
> +	/* Get the actual VRAM size from the device */
> +	ret = synthvid_connect_vsp(hdev);
> +	if (ret) {
> +		drm_err(dev, "Failed to connect to vmbus.\n");
> +		goto err_hv_set_drv_data;
> +	}
> +
> +	if (efi_enabled(EFI_BOOT))
> +		ret = hyperv_get_vram_gen2(hv, hdev);
> +	else
> +		ret = hyperv_get_vram_gen1(hv);
> +
> +	if (ret)
> +		goto err_vmbus_close;
> +
> +	/*
> +	 * Should be done only once during init and resume. Failing to update
> +	 * vram location is not fatal. Device will update dirty area till
> +	 * preferred resolution only.
> +	 */
> +	ret = synthvid_update_vram_location(hdev, hv->fb_base);
> +	if (ret)
> +		drm_warn(dev, "Failed to update vram location.\n");
> +
> +	ret = hyperv_mode_config_init(hv);
> +	if (ret)
> +		goto err_vmbus_close;
> +
> +	ret = drm_dev_register(dev, 0);
> +	if (ret) {
> +		drm_err(dev, "Failed to register drm driver.\n");
> +		goto err_vmbus_close;
> +	}
> +
> +	drm_fbdev_generic_setup(dev, 0);
> +
> +	return 0;
> +
> +err_vmbus_close:
> +	vmbus_close(hdev->channel);
> +err_hv_set_drv_data:
> +	hv_set_drvdata(hdev, NULL);
> +	return ret;
> +}
> +
> +static int hyperv_vmbus_remove(struct hv_device *hdev)
> +{
> +	struct drm_device *dev = hv_get_drvdata(hdev);
> +	struct hyperv_device *hv = to_hv(dev);
> +
> +	drm_dev_unplug(dev);
> +	drm_atomic_helper_shutdown(dev);
> +	vmbus_close(hdev->channel);
> +	hv_set_drvdata(hdev, NULL);
> +	vmbus_free_mmio(hv->mem->start, hv->fb_size);
> +
> +	return 0;
> +}
> +
> +static int hyperv_vmbus_suspend(struct hv_device *hdev)
> +{
> +	struct drm_device *dev = hv_get_drvdata(hdev);
> +	int ret;
> +
> +	ret = drm_mode_config_helper_suspend(dev);
> +
> +	vmbus_close(hdev->channel);
> +
> +	return ret;
> +}
> +
> +static int hyperv_vmbus_resume(struct hv_device *hdev)
> +{
> +	struct drm_device *dev = hv_get_drvdata(hdev);
> +	int ret;
> +
> +	ret = synthvid_connect_vsp(hdev);
> +	if (ret)
> +		return ret;
> +
> +	return drm_mode_config_helper_resume(dev);
> +}
> +
> +static const struct hv_vmbus_device_id hyperv_vmbus_tbl[] = {
> +	/* Synthetic Video Device GUID */
> +	{HV_SYNTHVID_GUID},
> +	{}
> +};
> +
> +static struct hv_driver hyperv_hv_driver = {
> +	.name = KBUILD_MODNAME,
> +	.id_table = hyperv_vmbus_tbl,
> +	.probe = hyperv_vmbus_probe,
> +	.remove = hyperv_vmbus_remove,
> +	.suspend = hyperv_vmbus_suspend,
> +	.resume = hyperv_vmbus_resume,
> +	.driver = {
> +		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
> +	},
> +};
> +
> +/* ---------------------------------------------------------------------- */
> +/* module init/exit                                                       */

The style of this comment looks out of place.

Best regards
Thomas

> +
> +static int __init hyperv_init(void)
> +{
> +	int ret;
> +
> +	ret = pci_register_driver(&hyperv_pci_driver);
> +	if (ret != 0)
> +		return ret;
> +
> +	return vmbus_driver_register(&hyperv_hv_driver);
> +}
> +
> +static void __exit hyperv_exit(void)
> +{
> +	vmbus_driver_unregister(&hyperv_hv_driver);
> +	pci_unregister_driver(&hyperv_pci_driver);
> +}
> +
> +module_init(hyperv_init);
> +module_exit(hyperv_exit);
> +
> +MODULE_DEVICE_TABLE(pci, hyperv_pci_tbl);
> +MODULE_DEVICE_TABLE(vmbus, hyperv_vmbus_tbl);
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Deepak Rawat <drawat.floss@gmail.com>");
> +MODULE_DESCRIPTION("DRM driver for hyperv synthetic video device");
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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