firewire: core: add local API to queue work item to workqueue specific to isochronous contexts

In the previous commit, the workqueue is added per the instance of fw_card
structure for isochronous contexts. The workqueue is designed to be used by
the implementation of fw_card_driver structure underlying the fw_card.

This commit adds some local APIs to be used by the implementation.

Tested-by: Edmund Raile <edmund.raile@protonmail.com>
Link: https://lore.kernel.org/r/20240904125155.461886-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

drivers/firewire/core-iso.c

@@ -211,21 +211,47 @@ EXPORT_SYMBOL(fw_iso_context_queue_flush);
 
 int fw_iso_context_flush_completions(struct fw_iso_context *ctx)
 {
+	int err;
+
 	trace_isoc_outbound_flush_completions(ctx);
 	trace_isoc_inbound_single_flush_completions(ctx);
 	trace_isoc_inbound_multiple_flush_completions(ctx);
 
-	return ctx->card->driver->flush_iso_completions(ctx);
+	might_sleep();
+
+	// Avoid dead lock due to programming mistake.
+	if (WARN_ON(current_work() == &ctx->work))
+		return 0;
+
+	disable_work_sync(&ctx->work);
+
+	err = ctx->card->driver->flush_iso_completions(ctx);
+
+	enable_work(&ctx->work);
+
+	return err;
 }
 EXPORT_SYMBOL(fw_iso_context_flush_completions);
 
 int fw_iso_context_stop(struct fw_iso_context *ctx)
 {
+	int err;
+
 	trace_isoc_outbound_stop(ctx);
 	trace_isoc_inbound_single_stop(ctx);
 	trace_isoc_inbound_multiple_stop(ctx);
 
-	return ctx->card->driver->stop_iso(ctx);
+	might_sleep();
+
+	// Avoid dead lock due to programming mistake.
+	if (WARN_ON(current_work() == &ctx->work))
+		return 0;
+
+	err = ctx->card->driver->stop_iso(ctx);
+
+	cancel_work_sync(&ctx->work);
+
+	return err;
 }
 EXPORT_SYMBOL(fw_iso_context_stop);
 

drivers/firewire/core.h

@@ -159,6 +159,16 @@ int fw_iso_buffer_alloc(struct fw_iso_buffer *buffer, int page_count);
 int fw_iso_buffer_map_dma(struct fw_iso_buffer *buffer, struct fw_card *card,
 			  enum dma_data_direction direction);
 
+static inline void fw_iso_context_init_work(struct fw_iso_context *ctx, work_func_t func)
+{
+	INIT_WORK(&ctx->work, func);
+}
+
+static inline void fw_iso_context_queue_work(struct fw_iso_context *ctx)
+{
+	queue_work(ctx->card->isoc_wq, &ctx->work);
+}
+
 
 /* -topology */
 

include/linux/firewire.h

@@ -511,6 +511,7 @@ union fw_iso_callback {
 
 struct fw_iso_context {
 	struct fw_card *card;
+	struct work_struct work;
 	int type;
 	int channel;
 	int speed;