Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
mailbox: add API to query available TX queue slots
Clients sometimes need to know whether the mailbox TX queue has room
before posting a new message. Rather than exposing internal queue state
through a struct field, provide a proper accessor function that returns
the number of available slots for a given channel.
This lets clients choose to back off when the queue is full instead of
hitting the -ENOBUFS error path and the misleading "Try increasing
MBOX_TX_QUEUE_LEN" warning.
Tested-by: Tanmay Shah <tanmay.shah@amd.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>
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drivers/mailbox/mailbox.c
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drivers/mailbox/mailbox.c
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EXPORT_SYMBOL_GPL(mbox_client_peek_data);
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/**
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* mbox_chan_tx_slots_available - Query the number of available TX queue slots.
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* @chan: Mailbox channel to query.
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*
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* Clients may call this to check how many messages can be queued via
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* mbox_send_message() before the channel's TX queue is full. This helps
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* clients avoid the -ENOBUFS error without needing to increase
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* MBOX_TX_QUEUE_LEN.
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* This can be called from atomic context.
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*
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* Return: Number of available slots in the channel's TX queue.
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*/
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unsigned int mbox_chan_tx_slots_available(struct mbox_chan *chan)
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{
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unsigned int ret;
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guard(spinlock_irqsave)(&chan->lock);
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ret = MBOX_TX_QUEUE_LEN - chan->msg_count;
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return ret;
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}
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EXPORT_SYMBOL_GPL(mbox_chan_tx_slots_available);
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/**
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* mbox_send_message - For client to submit a message to be
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* sent to the remote.
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* @chan: Mailbox channel assigned to this client.
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include/linux/mailbox_client.h
+1
include/linux/mailbox_client.h
···
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int mbox_flush(struct mbox_chan *chan, unsigned long timeout);
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void mbox_client_txdone(struct mbox_chan *chan, int r); /* atomic */
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bool mbox_client_peek_data(struct mbox_chan *chan); /* atomic */
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unsigned int mbox_chan_tx_slots_available(struct mbox_chan *chan); /* atomic */
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void mbox_free_channel(struct mbox_chan *chan); /* may sleep */
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#endif /* __MAILBOX_CLIENT_H */