firewire: add read_csr_reg driver callback

To prepare for the following additions of more OHCI-implemented CSR
registers, replace the get_cycle_time driver callback with a generic
CSR register callback.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

drivers/firewire/core-cdev.c

@@ -1044,7 +1044,7 @@ static int ioctl_get_cycle_timer2(struct client *client, union ioctl_arg *arg)
 
 	local_irq_disable();
 
-	cycle_time = card->driver->get_cycle_time(card);
+	cycle_time = card->driver->read_csr_reg(card, CSR_CYCLE_TIME);
 
 	switch (a->clk_id) {
 	case CLOCK_REALTIME:      getnstimeofday(&ts);                   break;

drivers/firewire/core-transaction.c

@@ -1025,7 +1025,8 @@ static void handle_registers(struct fw_card *card, struct fw_request *request,
 
 	case CSR_CYCLE_TIME:
 		if (TCODE_IS_READ_REQUEST(tcode) && length == 4)
-			*data = cpu_to_be32(card->driver->get_cycle_time(card));
+			*data = cpu_to_be32(card->driver->
+					read_csr_reg(card, CSR_CYCLE_TIME));
 		else
 			rcode = RCODE_TYPE_ERROR;
 		break;

drivers/firewire/core.h

@@ -75,7 +75,7 @@ struct fw_card_driver {
 	int (*enable_phys_dma)(struct fw_card *card,
 			       int node_id, int generation);
 
-	u32 (*get_cycle_time)(struct fw_card *card);
+	u32 (*read_csr_reg)(struct fw_card *card, int csr_offset);
 
 	struct fw_iso_context *
 	(*allocate_iso_context)(struct fw_card *card,

drivers/firewire/ohci.c

@@ -1939,9 +1939,8 @@ static u32 cycle_timer_ticks(u32 cycle_timer)
  * error.  (A PCI read should take at least 20 ticks of the 24.576 MHz timer to
  * execute, so we have enough precision to compute the ratio of the differences.)
  */
-static u32 ohci_get_cycle_time(struct fw_card *card)
+static u32 get_cycle_time(struct fw_ohci *ohci)
 {
-	struct fw_ohci *ohci = fw_ohci(card);
 	u32 c0, c1, c2;
 	u32 t0, t1, t2;
 	s32 diff01, diff12;
@@ -1970,6 +1969,20 @@ static u32 ohci_get_cycle_time(struct fw_card *card)
 	return c2;
 }
 
+static u32 ohci_read_csr_reg(struct fw_card *card, int csr_offset)
+{
+	struct fw_ohci *ohci = fw_ohci(card);
+
+	switch (csr_offset) {
+	case CSR_CYCLE_TIME:
+		return get_cycle_time(ohci);
+
+	default:
+		WARN_ON(1);
+		return 0;
+	}
+}
+
 static void copy_iso_headers(struct iso_context *ctx, void *p)
 {
 	int i = ctx->header_length;
@@ -2407,7 +2420,7 @@ static const struct fw_card_driver ohci_driver = {
 	.send_response		= ohci_send_response,
 	.cancel_packet		= ohci_cancel_packet,
 	.enable_phys_dma	= ohci_enable_phys_dma,
-	.get_cycle_time		= ohci_get_cycle_time,
+	.read_csr_reg		= ohci_read_csr_reg,
 
 	.allocate_iso_context	= ohci_allocate_iso_context,
 	.free_iso_context	= ohci_free_iso_context,