linux-kernel - Re: [PATCH V1 2/3] rpmsg: glink: Add support to handle signals command

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Message-ID: <YZ6P56yRP9TAtcqa@google.com>
Date:   Wed, 24 Nov 2021 11:17:59 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Deepak Kumar Singh <deesin@...eaurora.org>
Cc:     bjorn.andersson@...aro.org, swboyd@...omium.org,
        clew@...eaurora.org, mathieu.poirier@...aro.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Ohad Ben-Cohen <ohad@...ery.com>
Subject: Re: [PATCH V1 2/3] rpmsg: glink: Add support to handle signals
 command

On Thu, Sep 30, 2021 at 09:02:03PM +0530, Deepak Kumar Singh wrote:
> Remote peripherals send signal notifications over glink with commandID 15.
> 
> Add support to send and receive the signal command and convert the signals
> from NATIVE to TIOCM while receiving and vice versa while sending.
> 
> Signed-off-by: Chris Lew <clew@...eaurora.org>
> Signed-off-by: Deepak Kumar Singh <deesin@...eaurora.org>
> ---
>  drivers/rpmsg/qcom_glink_native.c | 75 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 75 insertions(+)
> 
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index 05533c7..384fcd2 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
>
> ...
>
> +static int qcom_glink_handle_signals(struct qcom_glink *glink,
> +				     unsigned int rcid, unsigned int sigs)
> +{
> +	struct glink_channel *channel;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&glink->idr_lock, flags);
> +	channel = idr_find(&glink->rcids, rcid);
> +	spin_unlock_irqrestore(&glink->idr_lock, flags);
> +	if (!channel) {
> +		dev_err(glink->dev, "signal for non-existing channel\n");
> +		return -EINVAL;
> +	}
> +
> +	/* convert signals from NATIVE to TIOCM */
> +	if (sigs & NATIVE_DTR_SIG)
> +		sigs |= TIOCM_DSR;
> +	if (sigs & NATIVE_CTS_SIG)
> +		sigs |= TIOCM_CTS;
> +	if (sigs & NATIVE_CD_SIG)
> +		sigs |= TIOCM_CD;
> +	if (sigs & NATIVE_RI_SIG)
> +		sigs |= TIOCM_RI;
> +	sigs &= 0x0fff;

'sigs' is only used when the channel has a signal handler, hence you could
return before the above block if there is no signal handler and remove the
condition below.

> +
> +	if (channel->ept.sig_cb)
> +		channel->ept.sig_cb(channel->ept.rpdev, channel->ept.priv, sigs);
> +
> +	return 0;
> +}