Re: [PATCH v3 1/3] drm: add SimpleDRM driver

Noralf Trønnes
2016-08-16T12:58:47Z

Den 15.08.2016 08:59, skrev Daniel Vetter:
> On Sun, Aug 14, 2016 at 06:52:04PM +0200, Noralf Trønnes wrote:
>> The SimpleDRM driver binds to simple-framebuffer devices and provides a
>> DRM/KMS API. It provides only a single CRTC+encoder+connector combination
>> plus one initial mode.
>>
>> Userspace can create dumb-buffers which can be blit into the real
>> framebuffer similar to UDL. No access to the real framebuffer is allowed
>> (compared to earlier version of this driver) to avoid security issues.
>> Furthermore, this way we can support arbitrary modes as long as we have a
>> conversion-helper.
>>
>> The driver was originally written by David Herrmann in 2014.
>> My main contribution is to make use of drm_simple_kms_helper and
>> rework the probe path to avoid use of the deprecated drm_platform_init()
>> and drm_driver.{load,unload}().
>> Additions have also been made for later changes to the Device Tree binding
>> document, like support for clocks, regulators and having the node under
>> /chosen. This code was lifted verbatim from simplefb.c.
>>
>> Cc: dh.herrmann@gmail.com
>> Cc: libv@skynet.be
>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

<snip>

>> diff --git a/drivers/gpu/drm/simpledrm/simpledrm_gem.c b/drivers/gpu/drm/simpledrm/simpledrm_gem.c
>> new file mode 100644
>> index 0000000..81bd7c5
>> --- /dev/null
>> +++ b/drivers/gpu/drm/simpledrm/simpledrm_gem.c

<snip>

>> +struct sdrm_gem_object *sdrm_gem_alloc_object(struct drm_device *ddev,
>> + size_t size)
>> +{
>> + struct sdrm_gem_object *obj;
>> +
>> + WARN_ON(!size || (size & ~PAGE_MASK) != 0);
>> +
>> + obj = kzalloc(sizeof(*obj), GFP_KERNEL);
>> + if (!obj)
>> + return NULL;
>> +
>> + drm_gem_private_object_init(ddev, &obj->base, size);
>> + return obj;
>> +}
>> +
>> +void sdrm_gem_free_object(struct drm_gem_object *gobj)
>> +{
>> + struct sdrm_gem_object *obj = to_sdrm_bo(gobj);
>> + struct drm_device *ddev = gobj->dev;
>> +
>> + if (obj->pages) {
>> + /* kill all user-space mappings */
>> + drm_vma_node_unmap(&gobj->vma_node,
>> + ddev->anon_inode->i_mapping);
>> + sdrm_gem_put_pages(obj);
>> + }
>> +
>> + if (gobj->import_attach)
>> + drm_prime_gem_destroy(gobj, obj->sg);
>> +
>> + drm_gem_free_mmap_offset(gobj);
>> + drm_gem_object_release(gobj);
>> + kfree(obj);
>> +}
>> +
>> +int sdrm_dumb_create(struct drm_file *dfile, struct drm_device *ddev,
>> + struct drm_mode_create_dumb *args)
>> +{
>> + struct sdrm_gem_object *obj;
>> + int r;
>> +
>> + if (args->flags)
>> + return -EINVAL;
>> +
>> + /* overflow checks are done by DRM core */
>> + args->pitch = (args->bpp + 7) / 8 * args->width;
>> + args->size = PAGE_ALIGN(args->pitch * args->height);
>> +
>> + obj = sdrm_gem_alloc_object(ddev, args->size);
>> + if (!obj)
>> + return -ENOMEM;
>> +
>> + r = drm_gem_handle_create(dfile, &obj->base, &args->handle);
>> + if (r) {
>> + drm_gem_object_unreference_unlocked(&obj->base);
>> + return r;
>> + }
>> +
>> + /* handle owns a reference */
>> + drm_gem_object_unreference_unlocked(&obj->base);
>> + return 0;
>> +}
>> +
>> +int sdrm_dumb_destroy(struct drm_file *dfile, struct drm_device *ddev,
>> + uint32_t handle)
>> +{
>> + return drm_gem_handle_delete(dfile, handle);
>> +}
> I wonder whether some dumb+gem helpers wouldn't be useful to roll out. At
> least drm_dumb_gem_destroy.c would be pretty simple.

There's already a drm_gem_dumb_destroy() in drm_gem.c

The drm_driver->gem_create_object callback makes it possible to do a
generic dumb create:

int drm_gem_dumb_create(struct drm_file *file, struct drm_device *dev,
struct drm_mode_create_dumb *args)
{
struct drm_gem_object *obj;
int ret;

if (!dev->driver->gem_create_object)
return -EINVAL;

args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
args->size = args->pitch * args->height;

obj = dev->driver->gem_create_object(dev, args->size);
if (!obj)
return -ENOMEM;

ret = drm_gem_handle_create(file, obj, &args->handle);
drm_gem_object_unreference_unlocked(obj);

return ret;
}
EXPORT_SYMBOL(drm_gem_dumb_create);

struct drm_gem_object *sdrm_gem_create_object(struct drm_device *ddev,
size_t size)
{
struct sdrm_gem_object *sobj;

sobj = sdrm_gem_alloc_object(ddev, size);
if (!sobj)
return ERR_PTR(-ENOMEM);

return &sobj->base;
}

>> +
>> +int sdrm_dumb_map_offset(struct drm_file *dfile, struct drm_device *ddev,
>> + uint32_t handle, uint64_t *offset)
>> +{
>> + struct drm_gem_object *gobj;
>> + int r;
>> +
>> + mutex_lock(&ddev->struct_mutex);
> There's still some struct mutex here.
>
>> +
>> + gobj = drm_gem_object_lookup(dfile, handle);
>> + if (!gobj) {
>> + r = -ENOENT;
>> + goto out_unlock;
>> + }
>> +
>> + r = drm_gem_create_mmap_offset(gobj);
>> + if (r)
>> + goto out_unref;
>> +
>> + *offset = drm_vma_node_offset_addr(&gobj->vma_node);
>> +
>> +out_unref:
>> + drm_gem_object_unreference(gobj);
>> +out_unlock:
>> + mutex_unlock(&ddev->struct_mutex);
>> + return r;
>> +}
>> +

Maybe this addition to drm_gem.c as well:

int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
uint32_t handle, uint64_t *offset)
{
struct drm_gem_object *obj;
int ret;

obj = drm_gem_object_lookup(file, handle);
if (!obj)
return -ENOENT;

ret = drm_gem_create_mmap_offset(obj);
if (ret)
goto out_unref;

*offset = drm_vma_node_offset_addr(&obj->vma_node);

out_unref:
drm_gem_object_unreference_unlocked(obj);

return ret;
}

>> +int sdrm_drm_mmap(struct file *filp, struct vm_area_struct *vma)
>> +{
>> + struct drm_file *priv = filp->private_data;
>> + struct drm_device *dev = priv->minor->dev;
>> + struct drm_vma_offset_node *node;
>> + struct drm_gem_object *gobj;
>> + struct sdrm_gem_object *obj;
>> + size_t size, i, num;
>> + int r;
>> +
>> + if (drm_device_is_unplugged(dev))
>> + return -ENODEV;
>> +
>> + drm_vma_offset_lock_lookup(dev->vma_offset_manager);
>> + node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
>> + vma->vm_pgoff,
>> + vma_pages(vma));
>> + drm_vma_offset_unlock_lookup(dev->vma_offset_manager);
>> +
>> + if (!drm_vma_node_is_allowed(node, filp))
>> + return -EACCES;
>> +
>> + gobj = container_of(node, struct drm_gem_object, vma_node);
>> + obj = to_sdrm_bo(gobj);
>> + size = drm_vma_node_size(node) << PAGE_SHIFT;
>> + if (size < vma->vm_end - vma->vm_start)
>> + return r;
>> +
>> + r = sdrm_gem_get_pages(obj);
>> + if (r < 0)
>> + return r;
>> +
>> + /* prevent dmabuf-imported mmap to user-space */
>> + if (!obj->pages)
>> + return -EACCES;
>> +
>> + vma->vm_flags |= VM_DONTEXPAND;
>> + vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
>> +
>> + num = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
>> + for (i = 0; i < num; ++i) {
>> + r = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
>> + obj->pages[i]);
>> + if (r < 0) {
>> + if (i > 0)
>> + zap_vma_ptes(vma, vma->vm_start, i * PAGE_SIZE);
>> + return r;
>> + }
>> + }
>> +
>> + return 0;
>> +}
> Why can't we just redirect to the underlying shmem mmap here (after
> argument checking)?

I don't know what that means, but looking at vc4 it seems I can use
drm_gem_mmap() to remove some boilerplate.

int sdrm_drm_mmap(struct file *filp, struct vm_area_struct *vma)
{
unsigned long vm_flags = vma->vm_flags;
struct sdrm_gem_object *sobj;
struct drm_gem_object *obj;
size_t i, num;
int r;

r = drm_gem_mmap(filp, vma);
if (r)
return r;

obj = vma->vm_private_data;

sobj = to_sdrm_bo(obj);

r = sdrm_gem_get_pages(obj);
if (r < 0)
return r;

/* prevent dmabuf-imported mmap to user-space */
if (!obj->pages)
return -EACCES;

/* drm_gem_mmap() sets flags that we don't want */
vma->vm_flags = vm_flags | VM_DONTEXPAND;
vma->vm_page_prot =
pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

num = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
for (i = 0; i < num; ++i) {
r = vm_insert_page(vma, vma->vm_start + i * PAGE_SIZE,
obj->pages[i]);
if (r < 0) {
if (i > 0)
zap_vma_ptes(vma, vma->vm_start, i * PAGE_SIZE);
return r;
}
}

return 0;
}

drm_gem_mmap() requires drm_driver->gem_vm_ops to be set:

const struct vm_operations_struct sdrm_gem_vm_ops = {
.open = drm_gem_vm_open,
.close = drm_gem_vm_close,
};

And browsing the code a bit more shows that tegra, udl, etnaviv and vgem
does the vm_insert_page() thing in the vm_operations_struct->fault()
handler.

So maybe this makes sense for simpledrm as well:

static int sdrm_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct drm_gem_object *obj = vma->vm_private_data;
struct sdrm_gem_object *sobj = to_sdrm_bo(obj);
loff_t num_pages;
pgoff_t offset;
int r;

if (!sobj->pages)
return VM_FAULT_SIGBUS;

offset = ((unsigned long)vmf->virtual_address - vma->vm_start) >>
PAGE_SHIFT;
num_pages = DIV_ROUND_UP(obj->base.size, PAGE_SIZE);
if (page_offset > num_pages)
return VM_FAULT_SIGBUS;

r = vm_insert_page(vma, (unsigned long)vmf->virtual_address,
sobj->pages[offset]);
switch (r) {
case -EAGAIN:
case 0:
case -ERESTARTSYS:
case -EINTR:
case -EBUSY:
return VM_FAULT_NOPAGE;

case -ENOMEM:
return VM_FAULT_OOM;
}

return VM_FAULT_SIGBUS;
}

Noralf.

>> +
>> +struct drm_gem_object *sdrm_gem_prime_import(struct drm_device *ddev,
>> + struct dma_buf *dma_buf)
>> +{
>> + struct dma_buf_attachment *attach;
>> + struct sdrm_gem_object *obj;
>> + struct sg_table *sg;
>> + int ret;
>> +
>> + /* need to attach */
>> + attach = dma_buf_attach(dma_buf, ddev->dev);
>> + if (IS_ERR(attach))
>> + return ERR_CAST(attach);
>> +
>> + get_dma_buf(dma_buf);
>> +
>> + sg = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>> + if (IS_ERR(sg)) {
>> + ret = PTR_ERR(sg);
>> + goto fail_detach;
>> + }
>> +
>> + /*
>> + * dma_buf_vmap() gives us a page-aligned mapping, so lets bump the
>> + * size of the dma-buf to the next page-boundary
>> + */
> dma_buf should be page-aligned already. Not sure we enforce that, but it's
> in practice a given.
>
>> + obj = sdrm_gem_alloc_object(ddev, PAGE_ALIGN(dma_buf->size));
>> + if (!obj) {
>> + ret = -ENOMEM;
>> + goto fail_unmap;
>> + }
>> +
>> + obj->sg = sg;
>> + obj->base.import_attach = attach;
>> +
>> + return &obj->base;
>> +
>> +fail_unmap:
>> + dma_buf_unmap_attachment(attach, sg, DMA_BIDIRECTIONAL);
>> +fail_detach:
>> + dma_buf_detach(dma_buf, attach);
>> + dma_buf_put(dma_buf);
>> + return ERR_PTR(ret);
>> +}
>> diff --git a/drivers/gpu/drm/simpledrm/simpledrm_kms.c b/drivers/gpu/drm/simpledrm/simpledrm_kms.c
>> new file mode 100644
>> index 0000000..00e50d9
>> --- /dev/null
>> +++ b/drivers/gpu/drm/simpledrm/simpledrm_kms.c
>> @@ -0,0 +1,258 @@
>> +/*
>> + * SimpleDRM firmware framebuffer driver
>> + * Copyright (c) 2012-2014 David Herrmann <dh.herrmann@gmail.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms of the GNU General Public License as published by the Free
>> + * Software Foundation; either version 2 of the License, or (at your option)
>> + * any later version.
>> + */
>> +
>> +#include <drm/drmP.h>
>> +#include <drm/drm_atomic_helper.h>
>> +#include <drm/drm_crtc.h>
>> +#include <drm/drm_crtc_helper.h>
>> +#include <drm/drm_gem.h>
>> +#include <drm/drm_simple_kms_helper.h>
>> +#include <linux/slab.h>
>> +
>> +#include "simpledrm.h"
>> +
>> +static const uint32_t sdrm_formats[] = {
>> + DRM_FORMAT_RGB565,
>> + DRM_FORMAT_ARGB8888,
>> + DRM_FORMAT_XRGB8888,
>> +};
>> +
>> +static int sdrm_conn_get_modes(struct drm_connector *conn)
>> +{
>> + struct sdrm_device *sdrm = conn->dev->dev_private;
>> + struct drm_display_mode *mode;
>> +
>> + mode = drm_cvt_mode(sdrm->ddev, sdrm->fb_width, sdrm->fb_height,
>> + 60, false, false, false);
>> + if (!mode)
>> + return 0;
>> +
>> + mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
>> + drm_mode_set_name(mode);
>> + drm_mode_probed_add(conn, mode);
>> +
>> + return 1;
>> +}
>> +
>> +static const struct drm_connector_helper_funcs sdrm_conn_hfuncs = {
>> + .get_modes = sdrm_conn_get_modes,
>> + .best_encoder = drm_atomic_helper_best_encoder,
>> +};
>> +
>> +static enum drm_connector_status sdrm_conn_detect(struct drm_connector *conn,
>> + bool force)
>> +{
>> + /*
>> + * We simulate an always connected monitor. simple-fb doesn't
>> + * provide any way to detect whether the connector is active. Hence,
>> + * signal DRM core that it is always connected.
>> + */
>> +
>> + return connector_status_connected;
>> +}
>> +
>> +static const struct drm_connector_funcs sdrm_conn_ops = {
>> + .dpms = drm_atomic_helper_connector_dpms,
>> + .reset = drm_atomic_helper_connector_reset,
>> + .detect = sdrm_conn_detect,
>> + .fill_modes = drm_helper_probe_single_connector_modes,
>> + .destroy = drm_connector_cleanup,
>> + .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
>> + .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
>> +};
>> +
>> +static inline struct sdrm_device *
>> +pipe_to_sdrm(struct drm_simple_display_pipe *pipe)
>> +{
>> + return container_of(pipe, struct sdrm_device, pipe);
>> +}
>> +
>> +static void sdrm_crtc_send_vblank_event(struct drm_crtc *crtc)
>> +{
>> + if (crtc->state && crtc->state->event) {
>> + spin_lock_irq(&crtc->dev->event_lock);
>> + drm_crtc_send_vblank_event(crtc, crtc->state->event);
>> + spin_unlock_irq(&crtc->dev->event_lock);
>> + crtc->state->event = NULL;
>> + }
>> +}
>> +
>> +void sdrm_display_pipe_update(struct drm_simple_display_pipe *pipe,
>> + struct drm_plane_state *plane_state)
>> +{
>> + struct drm_framebuffer *fb = pipe->plane.state->fb;
>> + struct sdrm_device *sdrm = pipe_to_sdrm(pipe);
>> +
>> + sdrm_crtc_send_vblank_event(&pipe->crtc);
>> +
>> + if (fb) {
>> + pipe->plane.fb = fb;
>> + sdrm_dirty_all_locked(sdrm);
>> + }
>> +}
>> +
>> +static void sdrm_display_pipe_enable(struct drm_simple_display_pipe *pipe,
>> + struct drm_crtc_state *crtc_state)
>> +{
>> + sdrm_crtc_send_vblank_event(&pipe->crtc);
>> +}
>> +
>> +static void sdrm_display_pipe_disable(struct drm_simple_display_pipe *pipe)
>> +{
>> + sdrm_crtc_send_vblank_event(&pipe->crtc);
>> +}
>> +
>> +static const struct drm_simple_display_pipe_funcs sdrm_pipe_funcs = {
>> + .update = sdrm_display_pipe_update,
>> + .enable = sdrm_display_pipe_enable,
>> + .disable = sdrm_display_pipe_disable,
>> +};
>> +
>> +static int sdrm_fb_create_handle(struct drm_framebuffer *fb,
>> + struct drm_file *dfile,
>> + unsigned int *handle)
>> +{
>> + struct sdrm_framebuffer *sfb = to_sdrm_fb(fb);
>> +
>> + return drm_gem_handle_create(dfile, &sfb->obj->base, handle);
>> +}
>> +
>> +static void sdrm_fb_destroy(struct drm_framebuffer *fb)
>> +{
>> + struct sdrm_framebuffer *sfb = to_sdrm_fb(fb);
>> +
>> + drm_framebuffer_cleanup(fb);
>> + drm_gem_object_unreference_unlocked(&sfb->obj->base);
>> + kfree(sfb);
>> +}
>> +
>> +static const struct drm_framebuffer_funcs sdrm_fb_ops = {
>> + .create_handle = sdrm_fb_create_handle,
>> + .dirty = sdrm_dirty,
>> + .destroy = sdrm_fb_destroy,
>> +};
>> +
>> +static struct drm_framebuffer *sdrm_fb_create(struct drm_device *ddev,
>> + struct drm_file *dfile,
>> + const struct drm_mode_fb_cmd2 *cmd)
>> +{
>> + struct sdrm_framebuffer *fb;
>> + struct drm_gem_object *gobj;
>> + u32 bpp, size;
>> + int ret;
>> + void *err;
>> +
>> + if (cmd->flags)
>> + return ERR_PTR(-EINVAL);
>> +
>> + gobj = drm_gem_object_lookup(dfile, cmd->handles[0]);
>> + if (!gobj)
>> + return ERR_PTR(-EINVAL);
>> +
>> + fb = kzalloc(sizeof(*fb), GFP_KERNEL);
>> + if (!fb) {
>> + err = ERR_PTR(-ENOMEM);
>> + goto err_unref;
>> + }
>> + fb->obj = to_sdrm_bo(gobj);
>> +
>> + fb->base.pitches[0] = cmd->pitches[0];
>> + fb->base.offsets[0] = cmd->offsets[0];
>> + fb->base.width = cmd->width;
>> + fb->base.height = cmd->height;
>> + fb->base.pixel_format = cmd->pixel_format;
>> + drm_fb_get_bpp_depth(cmd->pixel_format, &fb->base.depth,
>> + &fb->base.bits_per_pixel);
>> +
>> + /*
>> + * width/height are already clamped into min/max_width/height range,
>> + * so overflows are not possible
>> + */
>> +
>> + bpp = (fb->base.bits_per_pixel + 7) / 8;
>> + size = cmd->pitches[0] * cmd->height;
>> + if (!bpp ||
>> + bpp > 4 ||
>> + cmd->pitches[0] < bpp * fb->base.width ||
>> + cmd->pitches[0] > 0xffffU ||
>> + size + fb->base.offsets[0] < size ||
>> + size + fb->base.offsets[0] > fb->obj->base.size) {
>> + err = ERR_PTR(-EINVAL);
>> + goto err_free;
>> + }
>> +
>> + ret = drm_framebuffer_init(ddev, &fb->base, &sdrm_fb_ops);
>> + if (ret < 0) {
>> + err = ERR_PTR(ret);
>> + goto err_free;
>> + }
>> +
>> + DRM_DEBUG_KMS("[FB:%d] pixel_format: %s\n", fb->base.base.id,
>> + drm_get_format_name(fb->base.pixel_format));
>> +
>> + return &fb->base;
>> +
>> +err_free:
>> + kfree(fb);
>> +err_unref:
>> + drm_gem_object_unreference_unlocked(gobj);
>> +
>> + return err;
>> +}
>> +
>> +static const struct drm_mode_config_funcs sdrm_mode_config_ops = {
>> + .fb_create = sdrm_fb_create,
>> + .atomic_check = drm_atomic_helper_check,
>> + .atomic_commit = drm_atomic_helper_commit,
>> +};
>> +
>> +int sdrm_drm_modeset_init(struct sdrm_device *sdrm)
>> +{
>> + struct drm_connector *conn = &sdrm->conn;
>> + struct drm_device *ddev = sdrm->ddev;
>> + int ret;
>> +
>> + drm_mode_config_init(ddev);
>> + ddev->mode_config.min_width = sdrm->fb_width;
>> + ddev->mode_config.max_width = sdrm->fb_width;
>> + ddev->mode_config.min_height = sdrm->fb_height;
>> + ddev->mode_config.max_height = sdrm->fb_height;
>> + ddev->mode_config.preferred_depth = sdrm->fb_bpp;
>> + ddev->mode_config.funcs = &sdrm_mode_config_ops;
>> +
>> + drm_connector_helper_add(conn, &sdrm_conn_hfuncs);
>> + ret = drm_connector_init(ddev, conn, &sdrm_conn_ops,
>> + DRM_MODE_CONNECTOR_VIRTUAL);
>> + if (ret)
>> + goto err_cleanup;
>> +
>> + ret = drm_mode_create_dirty_info_property(ddev);
>> + if (ret)
>> + goto err_cleanup;
>> +
>> + drm_object_attach_property(&conn->base,
>> + ddev->mode_config.dirty_info_property,
>> + DRM_MODE_DIRTY_ON);
> dirty_info_property is gone.
>
>> +
>> + ret = drm_simple_display_pipe_init(ddev, &sdrm->pipe, &sdrm_pipe_funcs,
>> + sdrm_formats,
>> + ARRAY_SIZE(sdrm_formats), conn);
>> + if (ret)
>> + goto err_cleanup;
>> +
>> + drm_mode_config_reset(ddev);
>> +
>> + return 0;
>> +
>> +err_cleanup:
>> + drm_mode_config_cleanup(ddev);
>> +
>> + return ret;
>> +}
>> --
>> 2.8.2
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel