On Wed, Nov 21, 2012 at 09:03:38AM -0600, Rob Herring wrote:
On 11/21/2012 05:52 AM, Thierry Reding wrote:
On Wed, Nov 21, 2012 at 12:48:43PM +0100, Steffen Trumtrar wrote:
Hi!
On Wed, Nov 21, 2012 at 10:12:43AM +0000, Manjunathappa, Prakash wrote:
Hi Steffen,
On Tue, Nov 20, 2012 at 21:24:52, Steffen Trumtrar wrote:
+/**
- of_get_display_timings - parse all display_timing entries from a device_node
- @np: device_node with the subnodes
- **/
+struct display_timings *of_get_display_timings(const struct device_node *np) +{
- struct device_node *timings_np;
- struct device_node *entry;
- struct device_node *native_mode;
- struct display_timings *disp;
- if (!np) {
pr_err("%s: no devicenode given\n", __func__);return NULL;- }
- timings_np = of_find_node_by_name(np, "display-timings");
I get below build warnings on this line drivers/video/of_display_timing.c: In function 'of_get_display_timings': drivers/video/of_display_timing.c:109:2: warning: passing argument 1 of 'of_find_node_by_name' discards qualifiers from pointer target type include/linux/of.h:167:28: note: expected 'struct device_node *' but argument is of type 'const struct device_node *'
- of_display_timings_exists - check if a display-timings node is provided
- @np: device_node with the timing
- **/
+int of_display_timings_exists(const struct device_node *np) +{
- struct device_node *timings_np;
- if (!np)
return -EINVAL;- timings_np = of_parse_phandle(np, "display-timings", 0);
Also here: drivers/video/of_display_timing.c: In function 'of_display_timings_exists': drivers/video/of_display_timing.c:209:2: warning: passing argument 1 of 'of_parse_phandle' discards qualifiers from pointer target type include/linux/of.h:258:28: note: expected 'struct device_node *' but argument is of type 'const struct device_node *'
The warnings are because the of-functions do not use const pointers where they should. I had two options: don't use const pointers even if they should be and have no warnings or use const pointers and have a correct API. (Third option: send patches for of-functions). I chose the second option.
Maybe a better approach would be a combination of 1 and 3: don't use const pointers for struct device_node for now and bring the issue up with the OF maintainers, possibly with patches attached that fix the problematic functions.
Why does this need to be const? Since some DT functions increment refcount the node, I'm not sure that making struct device_node const in general is right thing to do. I do think it should be okay for of_parse_phandle.
I wasn't proposing to do it everywhere but only where possible. If the node is modified in some way then obviously it shouldn't be const.
Thierry