Hi Jassi,
Please find my comments below.
On 9/30/25 9:11 AM, Jassi Brar wrote:
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);
Ack here.
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;
It's not possible to make msg_slots_ro true Read-Only. Nothing prevents
clients to write to that variable as far as I know. Also, we have
msg_free variable that can be used to implement similar concept as
msg_slots_ro. But that also has same problem, not possible to implement
it in true read-only fashion.
I can instead implement API msg_queue_empty() and return msg_free
variable via that API.
-jassi
