Re: [igt-dev] [i-g-t, V3] lib/i915: Use FIXED mapping only for discrete memory

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Mon, 30 Aug 2021 23:00:13 -0700, Tejas Upadhyay wrote:
>
> The FIXED mapping is only used for discrete, and mapping type
> is pre-defined. This disables the other type of mmap
> offsets when discrete memory is used.
>
> Taken from kernel commit:
> commit 7961c5b60f23 ("drm/i915: Add TTM offset argument to mmap.")
>
> Changes since V2:
>	- Add previous logic check for GTT offset type - Ashutosh Dixit
>	- Added documentation for library API change - Daniel Vetter
> Changes since V1:
>         - Make logic more readable - Petri Latvala
>
> Signed-off-by: Tejas Upadhyay <tejaskumarx.surendrakumar.upadhyay@intel.com>
> ---
>  include/drm-uapi/i915_drm.h |  1 +
>  lib/i915/gem_mman.c         | 20 +++++++++++++++++++-
>  2 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/include/drm-uapi/i915_drm.h b/include/drm-uapi/i915_drm.h
> index a1c0030c..b46367f2 100644
> --- a/include/drm-uapi/i915_drm.h
> +++ b/include/drm-uapi/i915_drm.h
> @@ -871,6 +871,7 @@ struct drm_i915_gem_mmap_offset {
>  #define I915_MMAP_OFFSET_WC  1
>  #define I915_MMAP_OFFSET_WB  2
>  #define I915_MMAP_OFFSET_UC  3
> +#define I915_MMAP_OFFSET_FIXED 4

I don't believe we can add stuff to i915_drm.h like this we need to sync
with the kernel in drm-next? Also I915_MMAP_OFFSET_FIXED is already
available in lib/i915/i915_drm_local.h, so do we need to add this?

Matt, do you have any comments on this since you introduced the FIXED mmap
type? I am ok with the patch otherwise. Thanks.

>
>	/*
>	 * Zero-terminated chain of extensions.
> diff --git a/lib/i915/gem_mman.c b/lib/i915/gem_mman.c
> index 0406a0b9..aa9ac6f3 100644
> --- a/lib/i915/gem_mman.c
> +++ b/lib/i915/gem_mman.c
> @@ -73,9 +73,27 @@ bool gem_has_legacy_mmap(int fd)
>	return errno != EOPNOTSUPP;
>  }
>
> +/**
> + * gem_has_mmap_offset_type:
> + * @fd: open i915 drm file descriptor
> + * @*t: pointer to mmap_offset
> + *
> + * This functions checks the mmap offset type is supported or not.
> + * For discrete memory only FIXED mmap_offset type is supported
> + * and for non-discrete memory all other offset type except FIXED
> + * are supported.
> + *
> + * Returns: True if supported or False if not.
> + */
>  bool gem_has_mmap_offset_type(int fd, const struct mmap_offset *t)
>  {
> -	return gem_has_mmap_offset(fd) || t->type == I915_MMAP_OFFSET_GTT;
> +	if (gem_has_mmap_offset(fd))
> +		if (gem_has_lmem(fd))
> +			return t->type == I915_MMAP_OFFSET_FIXED;
> +		else
> +			return t->type != I915_MMAP_OFFSET_FIXED;
> +	else
> +		return t->type == I915_MMAP_OFFSET_GTT;
>  }
>
>  /**
> --
> 2.31.1
>