Re: [Embedded-pv-devel] [PATCH] drmif: add ABI for para-virtual DRM/KMS

[Julien Grall <julien.grall@xxxxxxx>]

Hi Oleksandr,

On 24/11/16 11:30, Oleksandr Andrushchenko wrote:
> This is the ABI for the two halves of a para-virtualized
> DRM/KMS driver.
>
> Signed-off-by: Oleksandr Andrushchenko <andr2000@xxxxxxxxx>
> Signed-off-by: Oleksandr Grytsov <al1img@xxxxxxxxx>
> ---
>  include/xen/interface/io/drmif.h       | 505 +++++++++++++++++++++++++++++++++
>  include/xen/interface/io/drmif_linux.h | 142 +++++++++
Same question as for sndif, any people who wants to use the PV driver 
for other OS than Linux will have to do it. So, may I ask why don't you 
write a platform agnostic header?
[...]

> diff --git a/include/xen/interface/io/drmif_linux.h 
> b/include/xen/interface/io/drmif_linux.h
> new file mode 100644
> index 0000000..7244148
> --- /dev/null
> +++ b/include/xen/interface/io/drmif_linux.h
> @@ -0,0 +1,142 @@
> +/******************************************************************************
> + * drmif_linux.h
> + *
> + *  Unified DRM-device I/O interface for Xen guest OSes
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to
> + * deal in the Software without restriction, including without limitation the
> + * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
> + * sell copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
> + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + *
> + * Copyright (C) 2016 EPAM Systems Inc.
> + *
> + * Authors: Oleksandr Andrushchenko <andr2000@xxxxxxxxx>
> + *          Oleksandr Grytsov <al1img@xxxxxxxxx>
> + */
> +
> +#ifndef __XEN_PUBLIC_IO_XENSND_LINUX_H__
> +#define __XEN_PUBLIC_IO_XENSND_LINUX_H__
> +
> +#include <xen/interface/io/ring.h>
> +#include <xen/interface/io/drmif.h>
> +#include <xen/interface/grant_table.h>
> +
> +struct xendrm_dumb_create_req {
> +       uint64_t dumb_cookie;
If I am not mistaken, this field will not be aligned to 64-bit in the 
final structure (xendrm_req). Which means that you will do an unaligned 
access. At best the processor will do an unaligned access but slowly 
(some processors will do 2 memory access), at worst the kernel will 
crash if alignment check was enabled.
So please re-order the field to avoid this drawbacks.

> +       uint32_t width;
> +       uint32_t height;
> +       uint32_t bpp;
> +       grant_ref_t gref_directory_start;
> +} __packed;
> +
> +struct xendrm_dumb_destroy_req {
> +       uint64_t dumb_cookie;
Ditto, although here it could be solved by adding a padding before hand.

> +} __packed;
> +
> +struct xendrm_fb_create_req {
> +       uint64_t dumb_cookie;
Ditto.

> +       uint64_t fb_cookie;
Ditto.

> +       uint32_t width;
> +       uint32_t height;
> +       uint32_t pixel_format;
> +} __packed;
> +
> +struct xendrm_fb_destroy_req {
> +       uint64_t fb_cookie;
Ditto, although there it could be solved by adding a padding before hand.

> +} __packed;
> +
> +struct xendrm_set_config_req {
> +       uint64_t fb_cookie;
Ditto.

> +       uint32_t x;
> +       uint32_t y;
> +       uint32_t width;
> +       uint32_t height;
> +       uint32_t bpp;
> +} __packed;
Regards,

--
Julien Grall

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