firewire: core: fix Model_ID in modalias

The modalias string of devices that represent units on a FireWire node
did not show Module_ID entries within unit directories.  This was
because firewire-core searched only the root directory of the
configuration ROM for a Model_ID entry.

We now search first the root directory, then the unit directory.  IOW
honor a unit directory's Model_ID if present, otherwise fall back to the
root directory's model ID (if present).

Furthermore, apply the same change to Vendor_ID.  This had the same
issue but it was less apparent because most devices provide Vendor_ID
only in the root directory.

And finally, also use this strategy for the remaining two IDs in the
modalias, Specifier_ID and Version.  It does not actually make sense to
look for them elsewhere than in the unit directory because they are
mandatory there.  However, a uniform search order simplifies the
implementation and has no adverse affect in practice.

Side notes:
  - The older counterpart of this, nodemgr.c of ieee1394, looked for
    Vendor_ID first in the root directory, then in the unit directory,
    and for Model_ID only in the unit directory.
  - There is a single mainline driver which requires Vendor_ID and
    Model_ID --- the firedtv driver.  This one worked because FireDTVs
    provide Vendor_ID in the root directory and Model_ID identically in
    root directory and unit directory.
  - Apart from firedtv, there are currently no drivers known to me
    (including userspace drivers) that look at the Vendor_ID or Model_ID
    of the modalias.

Reported-by: Maciej Żenczykowski <zenczykowski@gmail.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 14 insertions, 26 deletions

diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
index 014cabd3afda..c91d7179eb96 100644
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -180,44 +180,32 @@ static int fw_unit_match(struct device *dev, struct device_driver *drv)
         return 0;
 }
 
-static int get_modalias(struct fw_unit *unit, char *buffer, size_t buffer_size)
+static void get_modalias_ids(const u32 *directory, int *id)
 {
-        struct fw_device *device = fw_parent_device(unit);
         struct fw_csr_iterator ci;
-
         int key, value;
-        int vendor = 0;
-        int model = 0;
-        int specifier_id = 0;
-        int version = 0;
 
-        fw_csr_iterator_init(&ci, &device->config_rom[5]);
+        fw_csr_iterator_init(&ci, directory);
         while (fw_csr_iterator_next(&ci, &key, &value)) {
                 switch (key) {
-                case CSR_VENDOR:
-                        vendor = value;
-                        break;
-                case CSR_MODEL:
-                        model = value;
-                        break;
+                case CSR_VENDOR:        id[0] = value; break;
+                case CSR_MODEL:         id[1] = value; break;
+                case CSR_SPECIFIER_ID:  id[2] = value; break;
+                case CSR_VERSION:       id[3] = value; break;
                 }
         }
+}
 
-        fw_csr_iterator_init(&ci, unit->directory);
-        while (fw_csr_iterator_next(&ci, &key, &value)) {
-                switch (key) {
-                case CSR_SPECIFIER_ID:
-                        specifier_id = value;
-                        break;
-                case CSR_VERSION:
-                        version = value;
-                        break;
-                }
-        }
+static int get_modalias(struct fw_unit *unit, char *buffer, size_t buffer_size)
+{
+        int id[] = {0, 0, 0, 0};
+
+        get_modalias_ids(&fw_parent_device(unit)->config_rom[5], id);
+        get_modalias_ids(unit->directory, id);
 
         return snprintf(buffer, buffer_size,
                         "ieee1394:ven%08Xmo%08Xsp%08Xver%08X",
-                        vendor, model, specifier_id, version);
+                        id[0], id[1], id[2], id[3]);
 }
 
 static int fw_unit_uevent(struct device *dev, struct kobj_uevent_env *env)