firewire: fix use of multiple AV/C devices, allow multiple FCP listeners

Control of more than one AV/C device at once --- e.g. camcorders, tape
decks, audio devices, TV tuners --- failed or worked only unreliably,
depending on driver implementation.  This affected kernelspace and
userspace drivers alike and was caused by firewire-core's inability to
accept multiple registrations of FCP listeners.

The fix allows multiple address handlers to be registered for the FCP
command and response registers.  When a request for these registers is
received, all handlers are invoked, and the Firewire response is
generated by the core and not by any handler.

The cdev API does not change, i.e., userspace is still expected to send
a response for FCP requests; this response is silently ignored.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (changelog, rebased, whitespace)

2 files changed, 112 insertions, 32 deletions

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index 231e6ee5ba43..2cb22d160f6e 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -601,8 +601,9 @@ static void release_request(struct client *client,
         struct inbound_transaction_resource *r = container_of(resource,
                         struct inbound_transaction_resource, resource);
 
-        fw_send_response(client->device->card, r->request,
-                         RCODE_CONFLICT_ERROR);
+        if (r->request)
+                fw_send_response(client->device->card, r->request,
+                                 RCODE_CONFLICT_ERROR);
         kfree(r);
 }
 
@@ -645,7 +646,8 @@ static void handle_request(struct fw_card *card, struct fw_request *request,
  failed:
         kfree(r);
         kfree(e);
-        fw_send_response(card, request, RCODE_CONFLICT_ERROR);
+        if (request)
+                fw_send_response(card, request, RCODE_CONFLICT_ERROR);
 }
 
 static void release_address_handler(struct client *client,
@@ -715,15 +717,17 @@ static int ioctl_send_response(struct client *client, void *buffer)
 
         r = container_of(resource, struct inbound_transaction_resource,
                          resource);
-        if (request->length < r->length)
-                r->length = request->length;
-
-        if (copy_from_user(r->data, u64_to_uptr(request->data), r->length)) {
-                ret = -EFAULT;
-                goto out;
+        if (r->request) {
+                if (request->length < r->length)
+                        r->length = request->length;
+                if (copy_from_user(r->data, u64_to_uptr(request->data),
+                                   r->length)) {
+                        ret = -EFAULT;
+                        goto out;
+                }
+                fw_send_response(client->device->card, r->request,
+                                 request->rcode);
         }
-
-        fw_send_response(client->device->card, r->request, request->rcode);
  out:
         kfree(r);
 
diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c
index 842739df23e2..495849eb13cc 100644
--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -432,14 +432,20 @@ static struct fw_address_handler *lookup_overlapping_address_handler(
         return NULL;
 }
 
+static bool is_enclosing_handler(struct fw_address_handler *handler,
+                                 unsigned long long offset, size_t length)
+{
+        return handler->offset <= offset &&
+                offset + length <= handler->offset + handler->length;
+}
+
 static struct fw_address_handler *lookup_enclosing_address_handler(
         struct list_head *list, unsigned long long offset, size_t length)
 {
         struct fw_address_handler *handler;
 
         list_for_each_entry(handler, list, link) {
-                if (handler->offset <= offset &&
-                    offset + length <= handler->offset + handler->length)
+                if (is_enclosing_handler(handler, offset, length))
                         return handler;
         }
 
@@ -465,6 +471,12 @@ const struct fw_address_region fw_unit_space_region =
         { .start = 0xfffff0000900ULL, .end = 0x1000000000000ULL, };
 #endif  /*  0  */
 
+static bool is_in_fcp_region(u64 offset, size_t length)
+{
+        return offset >= (CSR_REGISTER_BASE | CSR_FCP_COMMAND) &&
+                offset + length <= (CSR_REGISTER_BASE | CSR_FCP_END);
+}
+
 /**
  * fw_core_add_address_handler - register for incoming requests
  * @handler: callback
@@ -477,8 +489,11 @@ const struct fw_address_region fw_unit_space_region =
  * give the details of the particular request.
  *
  * Return value:  0 on success, non-zero otherwise.
+ *
  * The start offset of the handler's address region is determined by
  * fw_core_add_address_handler() and is returned in handler->offset.
+ *
+ * Address allocations are exclusive, except for the FCP registers.
  */
 int fw_core_add_address_handler(struct fw_address_handler *handler,
                                 const struct fw_address_region *region)
@@ -498,10 +513,12 @@ int fw_core_add_address_handler(struct fw_address_handler *handler,
 
         handler->offset = region->start;
         while (handler->offset + handler->length <= region->end) {
-                other =
-                    lookup_overlapping_address_handler(&address_handler_list,
-                                                       handler->offset,
-                                                       handler->length);
+                if (is_in_fcp_region(handler->offset, handler->length))
+                        other = NULL;
+                else
+                        other = lookup_overlapping_address_handler
+                                        (&address_handler_list,
+                                         handler->offset, handler->length);
                 if (other != NULL) {
                         handler->offset += other->length;
                 } else {
@@ -668,6 +685,9 @@ static struct fw_request *allocate_request(struct fw_packet *p)
 void fw_send_response(struct fw_card *card,
                       struct fw_request *request, int rcode)
 {
+        if (WARN_ONCE(!request, "invalid for FCP address handlers"))
+                return;
+
         /* unified transaction or broadcast transaction: don't respond */
         if (request->ack != ACK_PENDING ||
             HEADER_DESTINATION_IS_BROADCAST(request->request_header[0])) {
@@ -686,26 +706,15 @@ void fw_send_response(struct fw_card *card,
 }
 EXPORT_SYMBOL(fw_send_response);
 
-void fw_core_handle_request(struct fw_card *card, struct fw_packet *p)
+static void handle_exclusive_region_request(struct fw_card *card,
+                                            struct fw_packet *p,
+                                            struct fw_request *request,
+                                            unsigned long long offset)
 {
         struct fw_address_handler *handler;
-        struct fw_request *request;
-        unsigned long long offset;
         unsigned long flags;
         int tcode, destination, source;
 
-        if (p->ack != ACK_PENDING && p->ack != ACK_COMPLETE)
-                return;
-
-        request = allocate_request(p);
-        if (request == NULL) {
-                /* FIXME: send statically allocated busy packet. */
-                return;
-        }
-
-        offset      =
-                ((unsigned long long)
-                 HEADER_GET_OFFSET_HIGH(p->header[1]) << 32) | p->header[2];
         tcode       = HEADER_GET_TCODE(p->header[0]);
         destination = HEADER_GET_DESTINATION(p->header[0]);
         source      = HEADER_GET_SOURCE(p->header[1]);
@@ -732,6 +741,73 @@ void fw_core_handle_request(struct fw_card *card, struct fw_packet *p)
                                           request->data, request->length,
                                           handler->callback_data);
 }
+
+static void handle_fcp_region_request(struct fw_card *card,
+                                      struct fw_packet *p,
+                                      struct fw_request *request,
+                                      unsigned long long offset)
+{
+        struct fw_address_handler *handler;
+        unsigned long flags;
+        int tcode, destination, source;
+
+        if ((offset != (CSR_REGISTER_BASE | CSR_FCP_COMMAND) &&
+             offset != (CSR_REGISTER_BASE | CSR_FCP_RESPONSE)) ||
+            request->length > 0x200) {
+                fw_send_response(card, request, RCODE_ADDRESS_ERROR);
+
+                return;
+        }
+
+        tcode       = HEADER_GET_TCODE(p->header[0]);
+        destination = HEADER_GET_DESTINATION(p->header[0]);
+        source      = HEADER_GET_SOURCE(p->header[1]);
+
+        if (tcode != TCODE_WRITE_QUADLET_REQUEST &&
+            tcode != TCODE_WRITE_BLOCK_REQUEST) {
+                fw_send_response(card, request, RCODE_TYPE_ERROR);
+
+                return;
+        }
+
+        spin_lock_irqsave(&address_handler_lock, flags);
+        list_for_each_entry(handler, &address_handler_list, link) {
+                if (is_enclosing_handler(handler, offset, request->length))
+                        handler->address_callback(card, NULL, tcode,
+                                                  destination, source,
+                                                  p->generation, p->speed,
+                                                  offset, request->data,
+                                                  request->length,
+                                                  handler->callback_data);
+        }
+        spin_unlock_irqrestore(&address_handler_lock, flags);
+
+        fw_send_response(card, request, RCODE_COMPLETE);
+}
+
+void fw_core_handle_request(struct fw_card *card, struct fw_packet *p)
+{
+        struct fw_request *request;
+        unsigned long long offset;
+
+        if (p->ack != ACK_PENDING && p->ack != ACK_COMPLETE)
+                return;
+
+        request = allocate_request(p);
+        if (request == NULL) {
+                /* FIXME: send statically allocated busy packet. */
+                return;
+        }
+
+        offset = ((u64)HEADER_GET_OFFSET_HIGH(p->header[1]) << 32) |
+                p->header[2];
+
+        if (!is_in_fcp_region(offset, request->length))
+                handle_exclusive_region_request(card, p, request, offset);
+        else
+                handle_fcp_region_request(card, p, request, offset);
+
+}
 EXPORT_SYMBOL(fw_core_handle_request);
 
 void fw_core_handle_response(struct fw_card *card, struct fw_packet *p)