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sna: Fix use of GETBLOB ioctl for grabbing the MST path 

Unlike the other drm getters, GETBLOB insists on the exact length rather
than being told the buffer size.

Reported-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
This commit is contained in:
Chris Wilson 2014-09-10 07:04:55 +01:00
parent 07fe45b84b
commit f39e1d19c1
1 changed files with 10 additions and 10 deletions
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20
src/sna/sna_display.c
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@ -3492,7 +3492,7 @@ static int name_from_path(struct sna *sna,
char *name)
{
struct drm_mode_get_blob blob;
char buf[32], *path = buf;
char *path;
int id;
id = find_property(sna, sna_output, "PATH");
@ -3502,20 +3502,19 @@ static int name_from_path(struct sna *sna,
VG_CLEAR(blob);
blob.blob_id = sna_output->prop_values[id];
blob.length = sizeof(buf)-1;
blob.data = (uintptr_t)path;
VG(memset(path, 0, blob.length));
blob.length = 0;
if (drmIoctl(sna->kgem.fd, DRM_IOCTL_MODE_GETPROPBLOB, &blob))
return 0;
if (blob.length >= sizeof(buf)) {
path = alloca(blob.length + 1);
do {
id = blob.length;
path = alloca(id + 1);
blob.data = (uintptr_t)path;
VG(memset(path, 0, blob.length));
DBG(("%s: reading %d bytes for path blob\n", __FUNCTION__, blob.length));
VG(memset(path, 0, id));
DBG(("%s: reading %d bytes for path blob\n", __FUNCTION__, id));
if (drmIoctl(sna->kgem.fd, DRM_IOCTL_MODE_GETPROPBLOB, &blob))
return 0;
}
} while (id != blob.length);
path[blob.length] = '\0'; /* paranoia */
DBG(("%s: PATH='%s'\n", __FUNCTION__, path));
@ -3540,7 +3539,8 @@ static int name_from_path(struct sna *sna,
for (n = 0; n < sna->mode.num_real_output; n++) {
if (to_sna_output(config->output[n])->id == id)
return snprintf(name, 32, "%s-%s", config->output[n]->name, c + 1);
return snprintf(name, 32, "%s-%s",
config->output[n]->name, c + 1);
}
}