lib/ioctl_wrappers: Keep IGT working without pread/pwrite ioctls

The general direction at this time is to phase out pread/write ioctls
and not support them in future products. This means IGT must handle
the absence of these ioctls. This patch does this by modifying
gem_read() and gem_write() to do the read/write using the pread/pwrite
ioctls first but when these ioctls are unavailable fall back to doing
the read/write using a combination of mmap and memcpy.

Callers who must absolutely use the pread/pwrite ioctls (such as tests
which test these ioctls or must otherwise only use the pread/pwrite
ioctls) must use gem_require_pread_pwrite() to skip when these ioctls
are not available.

v1: Removed __gem_pread, gem_pread, __gem_pwrite and gem_pwrite
    introduced previously since they are not necessary,
    gem_require_pread_pwrite is sufficient
v2: Fix CI failures in gem_advise and gen9_exec_parse by introducing
    gem_require_pread_pwrite
v3: Skip mmap for 0 length read/write's
v4: Remove redundant igt_assert's
v5: Re-run
v6: s/EOPNOTSUPP/-EOPNOTSUPP/
v7: Rebase on latest master, skip gem_exec_parallel@userptr with
    gem_require_pread_pwrite
v8: Re-run
v9: Rebase

Acked-by: Dave Airlie <airlied@redhat.com>
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/ioctl_wrappers.h b/lib/ioctl_wrappers.h
index 69e19841..9ea67365 100644
--- a/lib/ioctl_wrappers.h
+++ b/lib/ioctl_wrappers.h
@@ -71,6 +71,9 @@ int __gem_write(int fd, uint32_t handle, uint64_t offset, const void *buf, uint6
 void gem_write(int fd, uint32_t handle, uint64_t offset,  const void *buf, uint64_t length);
 int __gem_read(int fd, uint32_t handle, uint64_t offset, void *buf, uint64_t length);
 void gem_read(int fd, uint32_t handle, uint64_t offset, void *buf, uint64_t length);
+bool gem_has_pwrite(int fd);
+bool gem_has_pread(int fd);
+void gem_require_pread_pwrite(int fd);
 int __gem_set_domain(int fd, uint32_t handle, uint32_t read, uint32_t write);
 void gem_set_domain(int fd, uint32_t handle, uint32_t read, uint32_t write);
 int gem_wait(int fd, uint32_t handle, int64_t *timeout_ns);