linux-kernel - Re: [PATCH v2] serial: rp2: use 'request_firmware' instead of 'request_firmware

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Date:   Fri, 21 May 2021 08:51:16 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Zheyu Ma <zheyuma97@...il.com>
Cc:     cernekee@...il.com, jirislaby@...nel.org,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] serial: rp2: use 'request_firmware' instead of
 'request_firmware_nowait'

On Fri, May 21, 2021 at 06:08:43AM +0000, Zheyu Ma wrote:
> In 'rp2_probe', the driver registers 'rp2_uart_interrupt' then calls
> 'rp2_fw_cb' through 'request_firmware_nowait'. In 'rp2_fw_cb', if the
> firmware don't exists, function just return without initializing ports
> of 'rp2_card'. But now the interrupt handler function has been
> registered, and when an interrupt comes, 'rp2_uart_interrupt' may access
> those ports then causing NULL pointer dereference or other bugs.
> 
> Because the driver does some initialization work in 'rp2_fw_cb', in
> order to make the driver ready to handle interrupts, 'request_firmware'
> should be used instead of asynchronous 'request_firmware_nowait'.

You just now slowed down the probe function.  Are you _sure_ this is ok?

Do you have this hardware to test this?  If so, what is the init time
before and after this change?

thanks,

greg k-h