Messages in this thread | | | Subject | Re: [PATCH 3/3] mailbox: sunxi-msgbox: Add a new mailbox driver | From | Samuel Holland <> | Date | Wed, 28 Feb 2018 11:51:59 -0600 |
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Hi,
On 02/28/18 03:16, Jassi Brar wrote: > On Wed, Feb 28, 2018 at 7:57 AM, Samuel Holland <samuel@sholland.org> wrote: > .... > >> +/* >> + * The message box hardware provides 8 unidirectional channels. As the mailbox >> + * framework expects them to be bidirectional >> > That is incorrect. Mailbox framework does not require a channel to be > TX and RX capable.
Sorry, it would be more accurate to say that the intended mailbox _client_ expects the channels to be bidirectional.
> You should expose each channel as per its physical capability, let the > client configure it for direction (if its bidirectional) and acquire > separate channels for RX and TX if it needs to.
Is there any way for the mailbox framework to inform the client that a channel is uni/bidirectional? Or if the channel supports RX/TX specifically? I couldn't find any.
It looks like all of the clients assume one case or the other, based on the hardware they were initially designed to support. For example arm_scpi expects one channel per client, while ti_sci and st_remoteproc expect two separate RX and TX channels per client.
Since there's no API for the client to know the hardware properties, modifying arm_scpi to support unidirectional mailbox channels would break support for all existing bidirectional mailboxes.
To expose the physical channels individually, there would need to be an API to: a) Determine if a mailbox channel supports unidirectional or bidirectional operation. b) If a channel is unidirectional, determine which direction(s) it supports. c) If a unidirectional channel supports both directions, configure which direction it should run in.
Since that API doesn't currently exist, I wrote the driver to match what the intended client expected (as all other mailbox controller drivers currently do).
> Cheers!
Regards, Samuel
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