On Thu, Sep 25, 2025 at 1:51 PM Tanmay Shah <[email protected]> wrote:
>
> Sometimes clients need to know if mailbox queue is full or not before
> posting new message via mailbox. If mailbox queue is full clients can
> choose not to post new message. This doesn't mean current queue length
> should be increased, but clients may want to wait till previous Tx is
> done. This API can help avoid false positive warning from mailbox
> framework "Try increasing MBOX_TX_QUEUE_LEN".
>
> Signed-off-by: Tanmay Shah <[email protected]>
> ---
> drivers/mailbox/mailbox.c | 24 ++++++++++++++++++++++++
> drivers/remoteproc/xlnx_r5_remoteproc.c | 4 ++++
> include/linux/mailbox_client.h | 1 +
> 3 files changed, 29 insertions(+)
>
> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
> index 5cd8ae222073..7afdb2c9006d 100644
> --- a/drivers/mailbox/mailbox.c
> +++ b/drivers/mailbox/mailbox.c
> @@ -217,6 +217,30 @@ bool mbox_client_peek_data(struct mbox_chan *chan)
> }
> EXPORT_SYMBOL_GPL(mbox_client_peek_data);
>
> +/**
> + * mbox_queue_full - check if mailbox queue is full or not
> + * @chan: Mailbox channel assigned to this client.
> + *
> + * Clients can choose not to send new msg if mbox queue is full.
> + *
> + * Return: true if queue is full else false. < 0 for error
> + */
> +int mbox_queue_full(struct mbox_chan *chan)
> +{
> + unsigned long flags;
> + int res;
> +
> + if (!chan)
> + return -EINVAL;
> +
> + spin_lock_irqsave(&chan->lock, flags);
> + res = (chan->msg_count == (MBOX_TX_QUEUE_LEN - 1));
>
1) If we really need this, it should be
res = (chan->msg_count == MBOX_TX_QUEUE_LEN);
2) I am thinking instead, introduce a
struct mbox_client.msg_slots_ro;
Which is a read-only field for the client, denoting how many message
slots are currently available.
The mailbox api will always adjust it when msg_count changes...
chan->cl->msg_slots_ro = MBOX_TX_QUEUE_LEN - chan->msg_count;
-jassi
