linux-kernel - Re: [PATCH 1/2] cxl/mbox: Add background operation handling machinery

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Date:   Mon, 21 Nov 2022 13:48:04 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     linux-cxl@...r.kernel.org, dan.j.williams@...el.com,
        bwidawsk@...nel.org, ira.weiny@...el.com,
        alison.schofield@...el.com, vishal.l.verma@...el.com,
        a.manzanares@...sung.com, mcgrof@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] cxl/mbox: Add background operation handling machinery

On Thu, 25 Aug 2022, Jonathan Cameron wrote:

>> +/*
>> + * Ensure that ->mbox_send() can run safely when a background
>> + * command is running. If so, returns zero, otherwise -EBUSY.
>
>As above, I'm not sure this is necessary given you should get
>a sensible error code in response to any such message.
>E.g. media disabled.

So this is necessary to prevent mischief in the polling case
where you can have windows where the driver is out of sync
with the hardware - hw finishes async command but driver
(sleeping poller) has not acknowledged this. In the irq case,
yeah this would be redundant and not needed.

Thanks,
Davidlohr