The function of_match_device() should tell if a struct device matches an
of_device_id list and return the specific entry of that table matches the
device best.
The underlying __of_match_node() implements the wrong search algorithm. It
iterates over the list of of_device_ids, comparing the first compatible with
_all_ compatibles of the struct device, then the second compatible of
of_device_id and so on.
This leads to a problem, if the device has more than one compatible that match
the of_device_id list. The implemented search algorithm may find not the "best"
match. As the compatible list in the device is sorted from most to least
specific.
For example:
The imx28.dtsi gives this compatible string for its CAN core:
> compatible = "fsl,imx28-flexcan", "fsl,p1010-flexcan";
The flexcan driver defines:
> static const struct of_device_id flexcan_of_match[] = {
> { .compatible = "fsl,p1010-flexcan", .data = &fsl_p1010_devtype_data, },
> { .compatible = "fsl,imx28-flexcan", .data = &fsl_imx28_devtype_data, },
> { .compatible = "fsl,imx6q-flexcan", .data = &fsl_imx6q_devtype_data, },
> { /* sentinel */ },
> };
The "p1010" was the first Freescale SoC with the flexcan core. But this SoC has
a bug, so a workaround has to be enabled in the driver. The mx28 has this bug
fixed, so we don't need this quite costly workaround.
The __of_match_node() will compare:
from of_device_id from device
fsl,p1010-flexcan fsl,imx28-flexcan
fsl,p1010-flexcan fsl,p1010-flexcan -> MATCH
The of_match_device() function as it currently is implemented will always
return p1010 not the mx28.
This patch fixes the problem by exchanging outer and inner loop. The first
compatible of a device is compared against all compatible from the of_device_id
list, then the second device compatible and so on.
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
drivers/of/base.c | 40 +++++++++++++++++++++++++++++++++++-----
1 file changed, 35 insertions(+), 5 deletions(-)
diff --git a/drivers/of/base.c b/drivers/of/base.c
index 865d3f6..5bff2fe 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -349,6 +349,35 @@ static int __of_device_is_compatible(const struct device_node *device,
return 0;
}
+/** Returns the specific of_device_id, if the it matches one of the
+ * strings in the device's "compatible" property
+ */
+static
+const struct of_device_id *__of_device_matches_compatible(const struct device_node *device,
+ const struct of_device_id *matches)
+{
+ const struct of_device_id *m;
+ const char* cp;
+ int cplen, l;
+
+ cp = __of_get_property(device, "compatible", &cplen);
+ if (cp == NULL)
+ return NULL;
+ while (cplen > 0) {
+ m = matches;
+ while (m->compatible[0]) {
+ if (of_compat_cmp(cp, m->compatible, strlen(m->compatible)) == 0)
+ return m;
+ m++;
+ }
+ l = strlen(cp) + 1;
+ cp += l;
+ cplen -= l;
+ }
+
+ return NULL;
+}
+
/** Checks if the given "compat" string matches one of the strings in
* the device's "compatible" property
*/
@@ -717,22 +746,23 @@ const struct of_device_id *__of_match_node(const struct of_device_id *matches,
{
if (!matches)
return NULL;
-
- while (matches->name[0] || matches->type[0] || matches->compatible[0]) {
+ while (matches->name[0] || matches->type[0]) {
int match = 1;
+
if (matches->name[0])
match &= node->name
&& !strcmp(matches->name, node->name);
if (matches->type[0])
match &= node->type
&& !strcmp(matches->type, node->type);
- if (matches->compatible[0])
- match &= __of_device_is_compatible(node,
- matches->compatible);
if (match)
return matches;
matches++;
}
+
+ if (matches->compatible[0])
+ return __of_device_matches_compatible(node, matches);
+
return NULL;
}
--
1.8.4.rc3
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