On Tue, Nov 18, 2025 at 12:51 PM Tanmay Shah <[email protected]> wrote: > On 11/15/25 11:38 AM, Jassi Brar wrote: > > On Wed, Oct 15, 2025 at 10:27 AM Tanmay Shah <[email protected]> wrote: > >>>>> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c > >>>>> index 5cd8ae222073..c2e187aa5d22 100644 > >>>>> --- a/drivers/mailbox/mailbox.c > >>>>> +++ b/drivers/mailbox/mailbox.c > >>>>> @@ -35,6 +35,7 @@ static int add_to_rbuf(struct mbox_chan *chan, void > >>>>> *mssg) > >>>>> idx = chan->msg_free; > >>>>> chan->msg_data[idx] = mssg; > >>>>> chan->msg_count++; > >>>>> + chan->msg_slot_ro = (MBOX_TX_QUEUE_LEN - chan->msg_count); > >>>>> > >>>>> if (idx == MBOX_TX_QUEUE_LEN - 1) > >>>>> chan->msg_free = 0; > >>>>> @@ -70,6 +71,7 @@ static void msg_submit(struct mbox_chan *chan) > >>>>> if (!err) { > >>>>> chan->active_req = data; > >>>>> chan->msg_count--; > >>>>> + chan->msg_slot_ro = (MBOX_TX_QUEUE_LEN - > >>>>> chan->msg_count); > >>>>> > >>>> No, I had suggested adding this info in client structure. > >>>> There is no point in carrying msg_count and msg_slot_ro in mbox_chan. > >>>> The client needs this info but can/should not access the chan internals. > >>>> > >>> > >>> Hi Jassi, > >>> > >>> If I move msg_slot_ro to mbox_client that means, each channel needs its > >>> own client structure. But it is possible to map single client to > >>> multiple channels. > >>> > >>> How about if I rename msg_slot_ro to msg_slot_tx_ro -> that says this > >>> field should be used only for "tx" channel. > >>> > >>> Or is it must to map unique client data structure to each channel? If > >>> so, can I update mbox_client structure documentation ? > >>> > >> > >> Hi Jassi, > >> > >> I looked into this further. Looks like it's not possible to introduce > >> msg_slot_ro in the client data structure as of today. Because multiple > >> drivers are sharing same client for "tx" and "rx" both channels. > >> [references: 1, 2, 3] > >> > >> so, msg_slot_ro won't be calculated correctly I believe. > >> > > I don't see it. Can you please explain how the calculated value could be > > wrong? > > > > Hi Jassi, > > so on my platform I introduced some extra logs: > > [ 80.827479] mbox chan Rx send message > [ 80.827485] add_to_rbuf: &chan->cl->msg_slot_ro = 00000000ab5fa771, > msg slot ro = 19 > [ 80.827494] msg_submit: &chan->cl->msg_slot_ro = 00000000ab5fa771, > msg slot ro = 20 > [ 80.833064] mbox chan Tx send message > [ 80.833070] add_to_rbuf: &chan->cl->msg_slot_ro = 00000000ab5fa771, > msg slot ro = 19 > [ 80.833079] msg_submit: &chan->cl->msg_slot_ro = 00000000ab5fa771, > msg slot ro = 20 > [ 80.837486] mbox chan Rx send message > [ 80.837492] add_to_rbuf: &chan->cl->msg_slot_ro = 00000000ab5fa771, > msg slot ro = 19 > [ 80.837501] msg_submit: &chan->cl->msg_slot_ro = 00000000ab5fa771, > msg slot ro = 20 > > Tx and Rx both channels are updating same address of msg_slot_ro. If > user wants to check msg_slot_ro for Tx channel, then it is possible that > it was updated by Rx channel instead. Ideally there should be two copies > of msg_slot_ro, one for Tx and one for Rx channel. > > This happens because Tx and Rx both channels shares same client data > structure. > > Same can happen on other platforms as well. > The queue is only for TX. The received data is directly handed to the client. So RX path should not be modifying that queue availability variable.
thanks
