[PATCH 1/4 update] firewire: cdev: some clarifications to the APIdocumentation

From: Stefan Richter
Date: Sat Jul 17 2010 - 15:36:22 EST


Response events:
- are generated on more occasions than their documentation claimed.

CSR allocation:
- An already occupied CSR can be determined from errno==EBUSY.

Bus resets:
- Note that FW_CDEV_IOC_INITIATE_BUS_RESET is nonblocking and that the
client is not required to observe a grace period since kernels
2.6.36+ will enforce it now (commit 02d37bed).

- The possible values of fw_cdev_initiate_bus_reset.type are listed in
the kerneldoc comment already.

- Clarify that an application that uses FW_CDEV_IOC_ADD_DESCRIPTOR and
FW_CDEV_IOC_REMOVE_DESCRIPTOR does not have to issue a bus reset.

Isochronous I/O contexts:
- At most one can be created per open file descriptor.

Signed-off-by: Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx>
---

Update: Added the occupied CSR == EBUSY sentence.

include/linux/firewire-cdev.h | 33 +++++++++++++++++++++++++--------
1 file changed, 25 insertions(+), 8 deletions(-)

Index: b/include/linux/firewire-cdev.h
===================================================================
--- a/include/linux/firewire-cdev.h
+++ b/include/linux/firewire-cdev.h
@@ -89,8 +89,9 @@ struct fw_cdev_event_bus_reset {

/**
* struct fw_cdev_event_response - Sent when a response packet was received
- * @closure: See &fw_cdev_event_common;
- * set by %FW_CDEV_IOC_SEND_REQUEST ioctl
+ * @closure: See &fw_cdev_event_common; set by %FW_CDEV_IOC_SEND_REQUEST
+ * or %FW_CDEV_IOC_SEND_BROADCAST_REQUEST
+ * or %FW_CDEV_IOC_SEND_STREAM_PACKET ioctl
* @type: See &fw_cdev_event_common; always %FW_CDEV_EVENT_RESPONSE
* @rcode: Response code returned by the remote node
* @length: Data length, i.e. the response's payload size in bytes
@@ -100,6 +101,11 @@ struct fw_cdev_event_bus_reset {
* sent by %FW_CDEV_IOC_SEND_REQUEST ioctl. The payload data for responses
* carrying data (read and lock responses) follows immediately and can be
* accessed through the @data field.
+ *
+ * The event is also generated after conclusions of transactions that do not
+ * involve response packets. This includes unified write transactions,
+ * broadcast write transactions, and transmission of asynchronous stream
+ * packets. @rcode indicates success or failure of such transmissions.
*/
struct fw_cdev_event_response {
__u64 closure;
@@ -452,7 +458,9 @@ struct fw_cdev_send_response {
* range to be used for later deallocation of the range.
*
* The address range is allocated on all local nodes. The address allocation
- * is exclusive except for the FCP command and response registers.
+ * is exclusive except for the FCP command and response registers. If an
+ * exclusive address region is already in use, the ioctl fails with errno set
+ * to %EBUSY.
*/
struct fw_cdev_allocate {
__u64 offset;
@@ -480,9 +488,14 @@ struct fw_cdev_deallocate {
* Initiate a bus reset for the bus this device is on. The bus reset can be
* either the original (long) bus reset or the arbitrated (short) bus reset
* introduced in 1394a-2000.
+ *
+ * The ioctl returns immediately. A subsequent &fw_cdev_event_bus_reset
+ * indicates when the reset actually happened. Since ABI v4, this may be
+ * considerably later than the ioctl because the kernel ensures a grace period
+ * between subsequent bus resets as per IEEE 1394 bus management specification.
*/
struct fw_cdev_initiate_bus_reset {
- __u32 type; /* FW_CDEV_SHORT_RESET or FW_CDEV_LONG_RESET */
+ __u32 type;
};

/**
@@ -506,9 +519,10 @@ struct fw_cdev_initiate_bus_reset {
*
* @immediate, @key, and @data array elements are CPU-endian quadlets.
*
- * If successful, the kernel adds the descriptor and writes back a handle to the
- * kernel-side object to be used for later removal of the descriptor block and
- * immediate key.
+ * If successful, the kernel adds the descriptor and writes back a @handle to
+ * the kernel-side object to be used for later removal of the descriptor block
+ * and immediate key. The kernel will also generate a bus reset to signal the
+ * change of the configuration ROM to other nodes.
*
* This ioctl affects the configuration ROMs of all local nodes.
* The ioctl only succeeds on device files which represent a local node.
@@ -527,7 +541,8 @@ struct fw_cdev_add_descriptor {
* descriptor was added
*
* Remove a descriptor block and accompanying immediate key from the local
- * nodes' configuration ROMs.
+ * nodes' configuration ROMs. The kernel will also generate a bus reset to
+ * signal the change of the configuration ROM to other nodes.
*/
struct fw_cdev_remove_descriptor {
__u32 handle;
@@ -559,6 +574,8 @@ struct fw_cdev_remove_descriptor {
*
* Note that the effect of a @header_size > 4 depends on
* &fw_cdev_get_info.version, as documented at &fw_cdev_event_iso_interrupt.
+ *
+ * No more than one iso context can be created per fd.
*/
struct fw_cdev_create_iso_context {
__u32 type;

--
Stefan Richter
-=====-==-=- -=== =---=
http://arcgraph.de/sr/

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