[igt-dev] [PATCH] i915/tests/gem_exec_big: prefer PROT_WRITE

[Chris Wilson]

Quoting Matthew Auld (2020-01-24 16:41:31)
> Technically mmap__cpu and mmap__wc just ignore the prot value, so it
> doesn't really matter, but the intention is to have write access to the
> ptr, so make that clear. Also if the underlying mmap__wc were to at some
> point use mmap_offset where the prot is not ignored then we won't have
> any surprises.

The ptr here was just meant for cheaply reading back from the buffer to
verify the relocation took place. E.g., 

-static void exec1(int fd, uint32_t handle, uint64_t reloc_ofs, unsigned flags, char *ptr)
+static void exec1(int fd, uint32_t handle, uint64_t reloc_ofs, unsigned flags, const char *ptr)
 {
        struct drm_i915_gem_execbuffer2 execbuf;
        struct drm_i915_gem_exec_object2 gem_exec[1];
@@ -126,7 +126,7 @@ static void xchg_reloc(void *array, unsigned i, unsigned j)
        *b = tmp;
 }

-static void execN(int fd, uint32_t handle, uint64_t batch_size, unsigned flags, char *ptr)
+static void execN(int fd, uint32_t handle, uint64_t batch_size, unsigned flags, const char *ptr)
 {

What am I missing?
-Chris