sfc: Add support for 'extra' channel types

Abstract some of the channel operations to allow for 'extra'
channels that do not have RX or TX queues.

- Try to assign a channel to each extra channel type that is enabled
  for the NIC, but gracefully degrade if we can't allocate sufficient
  MSI-X vectors
- Allow each extra channel type to generate its own channel name
- Allow channel types to disable reallocation and reinitialisation
  of their channels
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/efx.h

@@ -95,6 +95,7 @@ static inline void efx_filter_rfs_expire(struct efx_channel *channel) {}
 #endif
 
 /* Channels */
+extern int efx_channel_dummy_op_int(struct efx_channel *channel);
 extern void efx_process_channel_now(struct efx_channel *channel);
 extern int
 efx_realloc_channels(struct efx_nic *efx, u32 rxq_entries, u32 txq_entries);

drivers/net/ethernet/sfc/net_driver.h

@@ -54,6 +54,7 @@
 
 #define EFX_MAX_CHANNELS 32U
 #define EFX_MAX_RX_QUEUES EFX_MAX_CHANNELS
+#define EFX_MAX_EXTRA_CHANNELS	0U
 
 /* Checksum generation is a per-queue option in hardware, so each
  * queue visible to the networking core is backed by two hardware TX
@@ -311,6 +312,7 @@ enum efx_rx_alloc_method {
  *
  * @efx: Associated Efx NIC
  * @channel: Channel instance number
+ * @type: Channel type definition
  * @enabled: Channel enabled indicator
  * @irq: IRQ number (MSI and MSI-X only)
  * @irq_moderation: IRQ moderation value (in hardware ticks)
@@ -341,6 +343,7 @@ enum efx_rx_alloc_method {
 struct efx_channel {
 	struct efx_nic *efx;
 	int channel;
+	const struct efx_channel_type *type;
 	bool enabled;
 	int irq;
 	unsigned int irq_moderation;
@@ -379,6 +382,26 @@ struct efx_channel {
 	struct efx_tx_queue tx_queue[EFX_TXQ_TYPES];
 };
 
+/**
+ * struct efx_channel_type - distinguishes traffic and extra channels
+ * @handle_no_channel: Handle failure to allocate an extra channel
+ * @pre_probe: Set up extra state prior to initialisation
+ * @post_remove: Tear down extra state after finalisation, if allocated.
+ *	May be called on channels that have not been probed.
+ * @get_name: Generate the channel's name (used for its IRQ handler)
+ * @copy: Copy the channel state prior to reallocation.  May be %NULL if
+ *	reallocation is not supported.
+ * @keep_eventq: Flag for whether event queue should be kept initialised
+ *	while the device is stopped
+ */
+struct efx_channel_type {
+	void (*handle_no_channel)(struct efx_nic *);
+	int (*pre_probe)(struct efx_channel *);
+	void (*get_name)(struct efx_channel *, char *buf, size_t len);
+	struct efx_channel *(*copy)(const struct efx_channel *);
+	bool keep_eventq;
+};
+
 enum efx_led_mode {
 	EFX_LED_OFF	= 0,
 	EFX_LED_ON	= 1,
@@ -631,6 +654,8 @@ struct efx_filter_state;
  * @rx_queue: RX DMA queues
  * @channel: Channels
  * @channel_name: Names for channels and their IRQs
+ * @extra_channel_types: Types of extra (non-traffic) channels that
+ *	should be allocated for this NIC
  * @rxq_entries: Size of receive queues requested by user.
  * @txq_entries: Size of transmit queues requested by user.
  * @next_buffer_table: First available buffer table id
@@ -723,6 +748,8 @@ struct efx_nic {
 
 	struct efx_channel *channel[EFX_MAX_CHANNELS];
 	char channel_name[EFX_MAX_CHANNELS][IFNAMSIZ + 6];
+	const struct efx_channel_type *
+	extra_channel_type[EFX_MAX_EXTRA_CHANNELS];
 
 	unsigned rxq_entries;
 	unsigned txq_entries;
@@ -921,6 +948,13 @@ efx_get_channel(struct efx_nic *efx, unsigned index)
 	     _channel = (_channel->channel + 1 < (_efx)->n_channels) ?	\
 		     (_efx)->channel[_channel->channel + 1] : NULL)
 
+/* Iterate over all used channels in reverse */
+#define efx_for_each_channel_rev(_channel, _efx)			\
+	for (_channel = (_efx)->channel[(_efx)->n_channels - 1];	\
+	     _channel;							\
+	     _channel = _channel->channel ?				\
+		     (_efx)->channel[_channel->channel - 1] : NULL)
+
 static inline struct efx_tx_queue *
 efx_get_tx_queue(struct efx_nic *efx, unsigned index, unsigned type)
 {