Message-ID: <BC25CBDD-D101-49DA-B10B-F47F1CAE2A6F@live.com>
Date: Tue, 18 Feb 2025 20:12:22 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: Thomas Zimmermann <tzimmermann@...e.de>
CC: "maarten.lankhorst@...ux.intel.com" <maarten.lankhorst@...ux.intel.com>,
	"mripard@...nel.org" <mripard@...nel.org>, "airlied@...il.com"
	<airlied@...il.com>, "simona@...ll.ch" <simona@...ll.ch>, Kerem Karabay
	<kekrby@...il.com>, Atharva Tiwari <evepolonium@...il.com>, Linux Kernel
 Mailing List <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 2/2] drm/tiny: add driver for Apple Touch Bars in x86 Macs

Hi

In continuation to my previous mail.

>> +
>> +static int appletbdrm_send_msg(struct appletbdrm_device *adev, u32 msg)
>> +{
>> + struct appletbdrm_msg_simple_request *request;
>> + int ret;
>> +
>> + request = kzalloc(sizeof(*request), GFP_KERNEL);
>> + if (!request)
>> + return -ENOMEM;
>> +
>> + request->header.unk_00 = cpu_to_le16(2);
>> + request->header.unk_02 = cpu_to_le16(0x1512);
>> + request->header.size = cpu_to_le32(sizeof(*request) - sizeof(request->header));
>> + request->msg = msg;
>> + request->size = request->header.size;
>> +
>> + ret = appletbdrm_send_request(adev, &request->header, sizeof(*request));
>> +
>> + kfree(request);
> 
> This is temporary data for the send operation and save to free here?

Probably yes. If I understand correctly, it’s needed to make the touchbar go into the display mode, from the hid keyboard mode.

We here are doing the same as the Windows driver [1] for this does.

[1] https://github.com/imbushuo/DFRDisplayKm/blob/master/src/DFRDisplayKm/include/Dfr.h#L3
> 
>> +
>> + return ret;
>> +}
>> +
>> +static int appletbdrm_clear_display(struct appletbdrm_device *adev)
>> +{
>> + return appletbdrm_send_msg(adev, APPLETBDRM_MSG_CLEAR_DISPLAY);
>> +}
>> +
>> +static int appletbdrm_signal_readiness(struct appletbdrm_device *adev)
>> +{
>> + return appletbdrm_send_msg(adev, APPLETBDRM_MSG_SIGNAL_READINESS);
>> +}
>> +
>> +static int appletbdrm_get_information(struct appletbdrm_device *adev)
>> +{
>> + struct appletbdrm_msg_information *info;
>> + struct drm_device *drm = &adev->drm;
>> + u8 bits_per_pixel;
>> + u32 pixel_format;
>> + int ret;
>> +
>> + info = kzalloc(sizeof(*info), GFP_KERNEL);
>> + if (!info)
>> + return -ENOMEM;
>> +
>> + ret = appletbdrm_send_msg(adev, APPLETBDRM_MSG_GET_INFORMATION);
>> + if (ret)
>> + return ret;
>> +
>> + ret = appletbdrm_read_response(adev, &info->header, sizeof(*info),
>> +        APPLETBDRM_MSG_GET_INFORMATION);
>> + if (ret)
>> + goto free_info;
>> +
>> + bits_per_pixel = info->bits_per_pixel;
>> + pixel_format = get_unaligned(&info->pixel_format);
>> +
>> + adev->width = get_unaligned_le32(&info->width);
>> + adev->height = get_unaligned_le32(&info->height);
>> +
>> + if (bits_per_pixel != APPLETBDRM_BITS_PER_PIXEL) {
>> + drm_err(drm, "Encountered unexpected bits per pixel value (%d)\n", bits_per_pixel);
>> + ret = -EINVAL;
>> + goto free_info;
>> + }
>> +
>> + if (pixel_format != APPLETBDRM_PIXEL_FORMAT) {
>> + drm_err(drm, "Encountered unknown pixel format (%p4ch)\n", &pixel_format);
>> + ret = -EINVAL;
>> + goto free_info;
>> + }
>> +
>> +free_info:
>> + kfree(info);
>> +
>> + return ret;
>> +}
>> +
>> +static u32 rect_size(struct drm_rect *rect)
>> +{
>> + return drm_rect_width(rect) * drm_rect_height(rect) * (APPLETBDRM_BITS_PER_PIXEL / 8);
>> +}
>> +
>> +static int appletbdrm_flush_damage(struct appletbdrm_device *adev,
>> +    struct drm_plane_state *old_state,
>> +    struct drm_plane_state *state)
>> +{
>> + struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(state);
>> + struct appletbdrm_fb_request_response *response;
>> + struct appletbdrm_fb_request_footer *footer;
>> + struct drm_atomic_helper_damage_iter iter;
>> + struct drm_framebuffer *fb = state->fb;
>> + struct appletbdrm_fb_request *request;
>> + struct drm_device *drm = &adev->drm;
>> + struct appletbdrm_frame *frame;
>> + u64 timestamp = ktime_get_ns();
>> + struct drm_rect damage;
>> + size_t frames_size = 0;
>> + size_t request_size;
>> + int ret;
>> +
>> + drm_atomic_helper_damage_iter_init(&iter, old_state, state);
>> + drm_atomic_for_each_plane_damage(&iter, &damage) {
>> + frames_size += struct_size(frame, buf, rect_size(&damage));
>> + }
>> +
>> + if (!frames_size)
>> + return 0;
>> +
>> + request_size = ALIGN(sizeof(*request) + frames_size + sizeof(*footer), 16);
>> +
>> + request = kzalloc(request_size, GFP_KERNEL);
>> + if (!request)
>> + return -ENOMEM;
>> +
>> + response = kzalloc(sizeof(*response), GFP_KERNEL);
>> + if (!response) {
>> + ret = -ENOMEM;
>> + goto free_request;
>> + }
> 
> This code runs in the middle of the atomic update. It's then too late to do error handling. If these allocs fail, the display hardware will remain in undefined state.
> 
> It is much preferable to allocate this memory in the atomic_check. To do so, you need a plane-state structure. Allocate the memory for request and response in the plane's atomic-check helper. If that fails, you can return an error there. Store the pointers and the request size in your plane-state structure and fetch them here.  The memory should later be freed in the plane's destroy callback. For an example, see how the ssd130x driver treats a buffer for a similar use case at [1].
> 
> [1] https://elixir.bootlin.com/linux/v6.13.2/source/drivers/gpu/drm/solomon/ssd130x.c#L1136
> 
> 
>> +
>> + ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
>> + if (ret) {
>> + drm_err(drm, "Failed to start CPU framebuffer access (%d)\n", ret);
>> + goto free_response;
>> + }
>> +
>> + request->header.unk_00 = cpu_to_le16(2);
>> + request->header.unk_02 = cpu_to_le16(0x12);
>> + request->header.unk_04 = cpu_to_le32(9);
>> + request->header.size = cpu_to_le32(request_size - sizeof(request->header));
>> + request->unk_10 = cpu_to_le16(1);
>> + request->msg_id = timestamp & 0xff;
>> +
>> + frame = (struct appletbdrm_frame *)request->data;
>> +
>> + drm_atomic_helper_damage_iter_init(&iter, old_state, state);
>> + drm_atomic_for_each_plane_damage(&iter, &damage) {
>> + struct iosys_map dst = IOSYS_MAP_INIT_VADDR(frame->buf);
>> + u32 buf_size = rect_size(&damage);
>> +
>> + /*
>> +  * The coordinates need to be translated to the coordinate
>> +  * system the device expects, see the comment in
>> +  * appletbdrm_setup_mode_config
>> +  */
>> + frame->begin_x = cpu_to_le16(damage.y1);
>> + frame->begin_y = cpu_to_le16(adev->height - damage.x2);
>> + frame->width = cpu_to_le16(drm_rect_height(&damage));
>> + frame->height = cpu_to_le16(drm_rect_width(&damage));
>> + frame->buf_size = cpu_to_le32(buf_size);
>> +
>> + ret = drm_fb_blit(&dst, NULL, DRM_FORMAT_BGR888,
>> +   &shadow_plane_state->data[0], fb, &damage, &shadow_plane_state->fmtcnv_state);
> 
> Can we void the use of drm_fb_blit()? Since you know all formats in advance, just do
> 
> switch (format)
> case XRGB8888: drm_fb_xrgb888_to_bgr888() break default:
>    drm_fb_memcpy() break }We use blit in simpledrm and ofdrm, where we don't know the formats and output buffers in advance. But it's really not so great in other drivers, I think.

I think you mean this:

#include <drm/drm_framebuffer.h>

		switch (fb->format->format) {
		case DRM_FORMAT_XRGB8888:
			drm_fb_xrgb8888_to_bgr888(&dst, NULL, &shadow_plane_state->data[0], fb, &damage, &shadow_plane_state->fmtcnv_state);
			break;
		default:
			drm_fb_memcpy(&dst, NULL, &shadow_plane_state->data[0], fb, &damage);
			break;
		}
>> + if (ret) {
>> + drm_err(drm, "Failed to copy damage clip (%d)\n", ret);
>> + goto end_fb_cpu_access;
>> + }
>> +
>> + frame = (void *)frame + struct_size(frame, buf, buf_size);
>> + }
>> +
>> + footer = (struct appletbdrm_fb_request_footer *)&request->data[frames_size];
>> +
>> + footer->unk_0c = cpu_to_le32(0xfffe);
>> + footer->unk_1c = cpu_to_le32(0x80001);
>> + footer->unk_34 = cpu_to_le32(0x80002);
>> + footer->unk_4c = cpu_to_le32(0xffff);
>> + footer->timestamp = cpu_to_le64(timestamp);
>> +
>> + ret = appletbdrm_send_request(adev, &request->header, request_size);
>> + if (ret)
>> + goto end_fb_cpu_access;
>> +
>> + ret = appletbdrm_read_response(adev, &response->header, sizeof(*response),
>> +        APPLETBDRM_MSG_UPDATE_COMPLETE);
>> + if (ret)
>> + goto end_fb_cpu_access;
>> +
>> + if (response->timestamp != footer->timestamp) {
>> + drm_err(drm, "Response timestamp (%llu) doesn't match request timestamp (%llu)\n",
>> + le64_to_cpu(response->timestamp), timestamp);
>> + goto end_fb_cpu_access;
>> + }
>> +
>> +end_fb_cpu_access:
>> + drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
>> +free_response:
>> + kfree(response);
>> +free_request:
>> + kfree(request);
>> +
>> + return ret;
>> +}
>> +
>> +static int appletbdrm_connector_helper_get_modes(struct drm_connector *connector)
>> +{
>> + struct appletbdrm_device *adev = drm_to_adev(connector->dev);
>> +
>> + return drm_connector_helper_get_modes_fixed(connector, &adev->mode);
>> +}
>> +
>> +static const u32 appletbdrm_primary_plane_formats[] = {
>> + DRM_FORMAT_BGR888,
>> + DRM_FORMAT_XRGB8888, /* emulated */
>> +};
>> +
>> +static int appletbdrm_primary_plane_helper_atomic_check(struct drm_plane *plane,
>> +    struct drm_atomic_state *state)
>> +{
>> + struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(state, plane);
>> + struct drm_crtc *new_crtc = new_plane_state->crtc;
>> + struct drm_crtc_state *new_crtc_state = NULL;
>> + int ret;
>> +
>> + if (new_crtc)
>> + new_crtc_state = drm_atomic_get_new_crtc_state(state, new_crtc);
>> +
>> + ret = drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
>> +   DRM_PLANE_NO_SCALING,
>> +   DRM_PLANE_NO_SCALING,
>> +   false, false);
>> + if (ret)
>> + return ret;
>> + else if (!new_plane_state->visible)
>> + return 0;
>> +
>> + return 0;
>> +}
>> +
>> +static void appletbdrm_primary_plane_helper_atomic_update(struct drm_plane *plane,
>> +      struct drm_atomic_state *old_state)
>> +{
>> + struct appletbdrm_device *adev = drm_to_adev(plane->dev);
>> + struct drm_device *drm = plane->dev;
>> + struct drm_plane_state *plane_state = plane->state;
>> + struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(old_state, plane);
>> + int idx;
> 
> plane_state->fb can be NULL if the plane's atomic_disable is not set. At a minimum you should check this first and return if so.
> 
> A better idea is to implement atomic_disable. You can try to move the code from appletbdrm_crtc_helper_atomic_disable() to the plane's atomic disable and remove the CRTC helper. That would put all drawing code into the plane. The CRTC is more about programming a display mode.
>> +
>> + if (!drm_dev_enter(drm, &idx))
>> + return;
>> +
>> + appletbdrm_flush_damage(adev, old_plane_state, plane_state);
>> +
>> + drm_dev_exit(idx);
>> +}
>> +
>> +static const struct drm_plane_helper_funcs appletbdrm_primary_plane_helper_funcs = {
>> + DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
>> + .atomic_check = appletbdrm_primary_plane_helper_atomic_check,
>> + .atomic_update = appletbdrm_primary_plane_helper_atomic_update,
>> +};
>> +
>> +static const struct drm_plane_funcs appletbdrm_primary_plane_funcs = {
>> + .update_plane = drm_atomic_helper_update_plane,
>> + .disable_plane = drm_atomic_helper_disable_plane,
>> + .destroy = drm_plane_cleanup,
>> + DRM_GEM_SHADOW_PLANE_FUNCS,
>> +};
>> +
>> +static enum drm_mode_status appletbdrm_crtc_helper_mode_valid(struct drm_crtc *crtc,
>> +   const struct drm_display_mode *mode)
>> +{
>> + struct appletbdrm_device *adev = drm_to_adev(crtc->dev);
>> +
>> + return drm_crtc_helper_mode_valid_fixed(crtc, mode, &adev->mode);
>> +}
>> +
>> +static void appletbdrm_crtc_helper_atomic_disable(struct drm_crtc *crtc,
>> +      struct drm_atomic_state *crtc_state)
>> +{
>> + struct appletbdrm_device *adev = drm_to_adev(crtc->dev);
>> + int idx;
>> +
>> + if (!drm_dev_enter(&adev->drm, &idx))
>> + return;
>> +
>> + appletbdrm_clear_display(adev);
>> +
>> + drm_dev_exit(idx);
>> +}
>> +
>> +static const struct drm_mode_config_funcs appletbdrm_mode_config_funcs = {
>> + .fb_create = drm_gem_fb_create_with_dirty,
>> + .atomic_check = drm_atomic_helper_check,
>> + .atomic_commit = drm_atomic_helper_commit,
>> +};
>> +
>> +static const struct drm_connector_funcs appletbdrm_connector_funcs = {
>> + .reset = drm_atomic_helper_connector_reset,
>> + .destroy = drm_connector_cleanup,
>> + .fill_modes = drm_helper_probe_single_connector_modes,
>> + .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
>> + .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
>> +};
>> +
>> +static const struct drm_connector_helper_funcs appletbdrm_connector_helper_funcs = {
>> + .get_modes = appletbdrm_connector_helper_get_modes,
>> +};
>> +
>> +static const struct drm_crtc_helper_funcs appletbdrm_crtc_helper_funcs = {
>> + .mode_valid = appletbdrm_crtc_helper_mode_valid,
>> + .atomic_disable = appletbdrm_crtc_helper_atomic_disable,
>> +};
>> +
>> +static const struct drm_crtc_funcs appletbdrm_crtc_funcs = {
>> + .reset = drm_atomic_helper_crtc_reset,
>> + .destroy = drm_crtc_cleanup,
>> + .set_config = drm_atomic_helper_set_config,
>> + .page_flip = drm_atomic_helper_page_flip,
>> + .atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
>> + .atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
>> +};
>> +
>> +static const struct drm_encoder_funcs appletbdrm_encoder_funcs = {
>> + .destroy = drm_encoder_cleanup,
>> +};
>> +
>> +DEFINE_DRM_GEM_FOPS(appletbdrm_drm_fops);
>> +
>> +static const struct drm_driver appletbdrm_drm_driver = {
>> + DRM_GEM_SHMEM_DRIVER_OPS,
> 
> For USB devices, we need special wiring to make PRIME work. The PRIME device must support DMA, but a USB device doesn't. So we pass the USB controller device instead. See [2] for what udl does and how it obtains dmadev.
> 
> [2] https://elixir.bootlin.com/linux/v6.14-rc3/source/drivers/gpu/drm/udl/udl_drv.c#L76

Disregard my previous reply for this. I believe you meant by this?:

—>8—
From b6fda730995b7f28374c1ff38778a6f3e6da65da Mon Sep 17 00:00:00 2001
From: Aditya Garg <gargaditya08@...e.com>
Date: Tue, 18 Feb 2025 22:47:44 +0530
Subject: [PATCH] prime

---
drivers/gpu/drm/tiny/appletbdrm.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/tiny/appletbdrm.c b/drivers/gpu/drm/tiny/appletbdrm.c
index f2d911325..b835063c2 100644
--- a/drivers/gpu/drm/tiny/appletbdrm.c
+++ b/drivers/gpu/drm/tiny/appletbdrm.c
@@ -118,6 +118,7 @@ struct appletbdrm_fb_request_response {

struct appletbdrm_device {
	struct device *dev;
+	struct device *dmadev;

	unsigned int in_ep;
	unsigned int out_ep;
@@ -521,10 +522,22 @@ static const struct drm_encoder_funcs appletbdrm_encoder_funcs = {
	.destroy = drm_encoder_cleanup,
};

+static struct drm_gem_object *appletbdrm_driver_gem_prime_import(struct drm_device *dev,
+								 struct dma_buf *dma_buf)
+{
+	struct appletbdrm_device *adev = drm_to_adev(dev);
+
+	if (!adev->dmadev)
+		return ERR_PTR(-ENODEV);
+
+	return drm_gem_prime_import_dev(dev, dma_buf, adev->dmadev);
+}
+
DEFINE_DRM_GEM_FOPS(appletbdrm_drm_fops);

static const struct drm_driver appletbdrm_drm_driver = {
	DRM_GEM_SHMEM_DRIVER_OPS,
+	.gem_prime_import	= appletbdrm_driver_gem_prime_import,
	.name			= "appletbdrm",
	.desc			= "Apple Touch Bar DRM Driver",
	.major			= 1,
-- 
2.43.0

—>8--
> 
>> + .name = "appletbdrm",
>> + .desc = "Apple Touch Bar DRM Driver",
>> + .date = "20230910",
> 
> The date field has been removed recently.
> 
>> + .major = 1,
>> + .minor = 0,
>> + .driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_ATOMIC,
>> + .fops = &appletbdrm_drm_fops,
>> +};
>> +
>> +static int appletbdrm_setup_mode_config(struct appletbdrm_device *adev)
>> +{
>> + struct drm_connector *connector = &adev->connector;
>> + struct drm_plane *primary_plane;
>> + struct drm_crtc *crtc;
>> + struct drm_encoder *encoder;
>> + struct drm_device *drm = &adev->drm;
>> + struct device *dev = adev->dev;
>> + int ret;
>> +
>> + ret = drmm_mode_config_init(drm);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to initialize mode configuration\n");
>> +
>> + primary_plane = &adev->primary_plane;
>> + ret = drm_universal_plane_init(drm, primary_plane, 0,
>> +        &appletbdrm_primary_plane_funcs,
>> +        appletbdrm_primary_plane_formats,
>> +        ARRAY_SIZE(appletbdrm_primary_plane_formats),
>> +        NULL,
>> +        DRM_PLANE_TYPE_PRIMARY, NULL);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to initialize universal plane object\n");
>> + drm_plane_helper_add(primary_plane, &appletbdrm_primary_plane_helper_funcs);
>> + drm_plane_enable_fb_damage_clips(primary_plane);
>> +
>> + crtc = &adev->crtc;
>> + ret = drm_crtc_init_with_planes(drm, crtc, primary_plane, NULL,
>> + &appletbdrm_crtc_funcs, NULL);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to initialize CRTC object\n");
>> + drm_crtc_helper_add(crtc, &appletbdrm_crtc_helper_funcs);
>> +
>> + encoder = &adev->encoder;
>> + ret = drm_encoder_init(drm, encoder, &appletbdrm_encoder_funcs,
>> +        DRM_MODE_ENCODER_DAC, NULL);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to initialize encoder\n");
>> + encoder->possible_crtcs = drm_crtc_mask(crtc);
>> +
>> + /*
>> +  * The coordinate system used by the device is different from the
>> +  * coordinate system of the framebuffer in that the x and y axes are
>> +  * swapped, and that the y axis is inverted; so what the device reports
>> +  * as the height is actually the width of the framebuffer and vice
>> +  * versa
>> +  */
>> + drm->mode_config.min_width = 0;
>> + drm->mode_config.min_height = 0;
> 
>> + drm->mode_config.max_width = max(adev->height, DRM_SHADOW_PLANE_MAX_WIDTH);
>> + drm->mode_config.max_height = max(adev->width, DRM_SHADOW_PLANE_MAX_HEIGHT);
> 
> This might not work correctly. To use those SHADOW_PLANE_MAX constants, you have to fixup the damage coordinates to account for changes to the plane coordinates. Simpledrm does that by intersecting damage with dst_clip. [3] You also have to put the result at the right place within the display.
> 
> [3] https://elixir.bootlin.com/linux/v6.14-rc3/source/drivers/gpu/drm/tiny/simpledrm.c#L646

This one is confusing for me. Could you clarify a bit more here?
> 
>> + drm->mode_config.preferred_depth = APPLETBDRM_BITS_PER_PIXEL;
>> + drm->mode_config.funcs = &appletbdrm_mode_config_funcs;
>> +
>> + adev->mode = (struct drm_display_mode) {
>> + DRM_MODE_INIT(60, adev->height, adev->width,
>> +       DRM_MODE_RES_MM(adev->height, 218),
>> +       DRM_MODE_RES_MM(adev->width, 218))
>> + };
>> +
>> + ret = drm_connector_init(drm, connector,
>> +  &appletbdrm_connector_funcs, DRM_MODE_CONNECTOR_USB);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to initialize connector\n");
>> +
>> + drm_connector_helper_add(connector, &appletbdrm_connector_helper_funcs);
>> +
>> + ret = drm_connector_set_panel_orientation(connector,
>> +   DRM_MODE_PANEL_ORIENTATION_RIGHT_UP);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to set panel orientation\n");
>> +
>> + connector->display_info.non_desktop = true;
>> + ret = drm_object_property_set_value(&connector->base,
>> +     drm->mode_config.non_desktop_property, true);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to set non-desktop property\n");
>> +
>> + ret = drm_connector_attach_encoder(connector, encoder);
>> +
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to initialize simple display pipe\n");
>> +
>> + drm_mode_config_reset(drm);
>> +
> 
> 
>> + ret = drm_dev_register(drm, 0);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to register DRM device\n");
> 
> This call does not belong to the mode-setting pipeline and belongs into appletbdrm_probe().

Moving this to appletbdrm_probe() again leads to a freezing Touch Bar. Maybe I am placing it at the wrong place?
> 
> 
>> +
>> + return 0;
>> +}
>> +
>> +static int appletbdrm_probe(struct usb_interface *intf,
>> +     const struct usb_device_id *id)
>> +{
>> + struct usb_endpoint_descriptor *bulk_in, *bulk_out;
>> + struct device *dev = &intf->dev;
>> + struct appletbdrm_device *adev;
>> + int ret;
>> +
>> + ret = usb_find_common_endpoints(intf->cur_altsetting, &bulk_in, &bulk_out, NULL, NULL);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to find bulk endpoints\n");
>> +
>> + adev = devm_drm_dev_alloc(dev, &appletbdrm_drm_driver, struct appletbdrm_device, drm);
>> + if (IS_ERR(adev))
>> + return PTR_ERR(adev);
>> +
>> + adev->dev = dev;
>> + adev->in_ep = bulk_in->bEndpointAddress;
>> + adev->out_ep = bulk_out->bEndpointAddress;
>> +
>> + usb_set_intfdata(intf, adev);
> 
> Rather set the DRM device here and fetch it in the callbacks below. At some point, we might be able to share some of those helpers among drivers.
> 
>> +
>> + ret = appletbdrm_get_information(adev);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to get display information\n");
>> +
>> + ret = appletbdrm_signal_readiness(adev);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to signal readiness\n");
>> +
> 
>> + ret = appletbdrm_clear_display(adev);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "Failed to clear display\n");
> 
> Clearing the display is not something usually done in probe. But I guess there's no better place. I'd do this as the final call in probe; after registering the device.  That way, it acts a bit like an in-kernel DRM client.
> 
> Best regards
> Thomas
> 
>> +
>> + return appletbdrm_setup_mode_config(adev);
>> +}
>> +
>> +static void appletbdrm_disconnect(struct usb_interface *intf)
>> +{
>> + struct appletbdrm_device *adev = usb_get_intfdata(intf);
>> + struct drm_device *drm = &adev->drm;
>> +
>> + drm_dev_unplug(drm);
>> + drm_atomic_helper_shutdown(drm);
>> +}
>> +
>> +static void appletbdrm_shutdown(struct usb_interface *intf)
>> +{
>> + struct appletbdrm_device *adev = usb_get_intfdata(intf);
>> +
>> + /*
>> +  * The framebuffer needs to be cleared on shutdown since its content
>> +  * persists across boots
>> +  */
>> + drm_atomic_helper_shutdown(&adev->drm);
>> +}
>> +
>> +static const struct usb_device_id appletbdrm_usb_id_table[] = {
>> + { USB_DEVICE_INTERFACE_CLASS(0x05ac, 0x8302, USB_CLASS_AUDIO_VIDEO) },
>> + {}
>> +};
>> +MODULE_DEVICE_TABLE(usb, appletbdrm_usb_id_table);
>> +
>> +static struct usb_driver appletbdrm_usb_driver = {
>> + .name = "appletbdrm",
>> + .probe = appletbdrm_probe,
>> + .disconnect = appletbdrm_disconnect,
>> + .shutdown = appletbdrm_shutdown,
>> + .id_table = appletbdrm_usb_id_table,
>> +};
>> +module_usb_driver(appletbdrm_usb_driver);
>> +
>> +MODULE_AUTHOR("Kerem Karabay <kekrby@...il.com>");
>> +MODULE_DESCRIPTION("Apple Touch Bar DRM Driver");
>> +MODULE_LICENSE("GPL");
> 
> -- 
> --
> 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)

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