23.06.2020 15:09, Mikko Perttunen пишет:
/* Command is an opcode gather from a GEM handle */ #define DRM_TEGRA_SUBMIT_COMMAND_GATHER 0 /* Command is an opcode gather from a user pointer */ #define DRM_TEGRA_SUBMIT_COMMAND_GATHER_UPTR 1 /* Command is a wait for syncpt fence completion */ #define DRM_TEGRA_SUBMIT_COMMAND_WAIT_SYNCPT 2 /* Command is a wait for SYNC_FILE FD completion */ #define DRM_TEGRA_SUBMIT_COMMAND_WAIT_SYNC_FILE 3 /* Command is a wait for DRM syncobj completion */ #define DRM_TEGRA_SUBMIT_COMMAND_WAIT_SYNCOBJ 4
/* * Allow driver to skip command execution if engine * was not accessed by another channel between * submissions. */ #define DRM_TEGRA_SUBMIT_CONTEXT_SETUP (1<<0)
struct drm_tegra_submit_command { __u16 type; __u16 flags;
Shouldn't the "packed" attribute be needed if a non-32bit aligned fields are used?
union { struct { /* GEM handle */ __u32 handle;
/* * Offset into GEM object in bytes. * Must be aligned by 4. */ __u64 offset;
64bits for a gather offset is a bit too much, in most cases gathers are under 4K.
u32 should be more than enough (maybe even u16 if offset is given in a dword granularity).
/* * Length of gather in bytes. * Must be aligned by 4. */ __u64 length;
u32/16
} gather;
struct { __u32 reserved[1];
/* * Pointer to gather data. * Must be aligned by 4 bytes. */ __u64 base; /* * Length of gather in bytes. * Must be aligned by 4. */ __u64 length; } gather_uptr;
What about to inline the UPTR gather data and relocs into the drm_tegra_submit_command[] buffer:
struct drm_tegra_submit_command { struct { u16 num_words; u16 num_relocs;
gather_data[]; drm_tegra_submit_relocation relocs[]; } gather_uptr; };
struct drm_tegra_channel_submit { __u32 num_syncpt_incrs; __u32 syncpt_idx;
__u64 commands_ptr; __u32 commands_size; ... };
struct drm_tegra_submit_command example[] = { cmd.gather_uptr{}, ... gather_data[], gather_relocs[], cmd.wait_syncpt{}, ... };
This way we will have only a single copy_from_user() for the whole cmdstream, which should be more efficient to do and nicer from both userspace and kernel perspectives in regards to forming and parsing the commands.