On 01/12/2012 12:00 PM, Simon Glass wrote:
> Some devices can deal with multiple compatible properties. The devices
> need to know which nodes to bind to which features. For example an
> I2C driver which supports two different controller types will want to
> know which type it is dealing with in each case.
>
> The new fdtdec_add_aliases_for_id() function deals with this by allowing
> the driver to search for additional compatible nodes for a different ID.
> It can then detect the new ones and perform appropriate processing.
>
> Another option considered was to return a tuple (node offset, compat id)
> and have the function be passed a list of compatible IDs. This is more
> overhead for the common case though. We may add such a function later if
> more drivers in U-Boot require it.
> +int fdtdec_add_aliases_for_id(const void *blob, const char *name,
> + enum fdt_compat_id id, int *node_list, int maxcount)
...
> @@ -232,11 +238,13 @@ int fdtdec_find_aliases_for_id(const void *blob, const
> char *name,
> * it as done.
> */
> if (fdtdec_get_is_enabled(blob, node)) {
> + if (node_list[number])
> + continue;
> node_list[number] = node;
> if (number >= num_found)
> num_found = number + 1;
> }
> - nodes[j] = 0;
> + nodes[found] = 0;
> }
>
> /* Add any nodes not mentioned by an alias */
Aren't those two changes really bug-fixes to the underlying patch rather
than part of this enhancement?
I'm not convinced this patch is correct in all cases. It'll probably
work fine for simply device-trees though. Consider the following case:
4 device nodes
A: compat=i2c alias for usb0
B: compat=i2c no alias
C: compat=i2c alias for usb2
D: compat=i2cx alias for usb1
First, we search for all compat=i2c, the list comes back:
0=A
1=B
2=C
Then we search for all compat=i2cx, the list comes back:
-1
-1
-1
D
So D's alias of 1 isn't honored even though if both IDs were searched
for together, it would have been.
Also, what about the scenario where a driver searches for both
nvidia,tegra20-i2c then later nvidia,tegra30-i2c, given that all the DT
nodes are probably compatible with both?
--
nvpublic
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