linux-kernel - Re: [PATCH 5/9] media: cros-ec-cec: Support multiple ports in MKBP cec

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Message-ID: <67a1657a-e8f4-683c-375d-5ca6b1e75b9a@xs4all.nl>
Date:   Mon, 21 Aug 2023 10:51:12 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Reka Norman <rekanorman@...omium.org>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        Daisuke Nojiri <dnojiri@...omium.org>,
        Stefan Adolfsson <sadolfsson@...gle.com>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH 5/9] media: cros-ec-cec: Support multiple ports in MKBP
 cec_events

Hi Reka,

On 14/08/2023 06:29, Reka Norman wrote:
> Use the top four bits of the cec_events MKBP event to store the port
> number.
> 
> Signed-off-by: Reka Norman <rekanorman@...omium.org>
> ---
> 
>  drivers/media/cec/platform/cros-ec/cros-ec-cec.c | 13 +++++++++++--
>  include/linux/platform_data/cros_ec_commands.h   | 10 ++++++++++
>  2 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/cec/platform/cros-ec/cros-ec-cec.c b/drivers/media/cec/platform/cros-ec/cros-ec-cec.c
> index d674a432dfdd..eb4b778f83e9 100644
> --- a/drivers/media/cec/platform/cros-ec/cros-ec-cec.c
> +++ b/drivers/media/cec/platform/cros-ec/cros-ec-cec.c
> @@ -77,8 +77,17 @@ static void handle_cec_message(struct cros_ec_cec *cros_ec_cec)
>  static void handle_cec_event(struct cros_ec_cec *cros_ec_cec)
>  {
>  	struct cros_ec_device *cros_ec = cros_ec_cec->cros_ec;
> -	uint32_t events = cros_ec->event_data.data.cec_events;
> -	struct cros_ec_cec_port *port = cros_ec_cec->ports[CEC_PORT];
> +	uint32_t cec_events = cros_ec->event_data.data.cec_events;
> +	int port_num = EC_MKBP_EVENT_CEC_GET_PORT(cec_events);
> +	uint32_t events = EC_MKBP_EVENT_CEC_GET_EVENTS(cec_events);
> +	struct cros_ec_cec_port *port;
> +
> +	if (port_num < 0 || port_num >= cros_ec_cec->num_ports) {

Since cec_events is unsigned, then I would also keep port_num unsigned.
Mixing signed and unsigned for bit shifting is a bit dangerous.

That will also mean that you can skip the 'port_num < 0' check.

Regards,

	Hans

> +		dev_err(cros_ec->dev,
> +			"received CEC event for invalid port %d\n", port_num);
> +		return;
> +	}
> +	port = cros_ec_cec->ports[port_num];
>  
>  	if (events & EC_MKBP_CEC_SEND_OK)
>  		cec_transmit_attempt_done(port->adap, CEC_TX_STATUS_OK);
> diff --git a/include/linux/platform_data/cros_ec_commands.h b/include/linux/platform_data/cros_ec_commands.h
> index 9a0c6e28f370..b7e8573a8a49 100644
> --- a/include/linux/platform_data/cros_ec_commands.h
> +++ b/include/linux/platform_data/cros_ec_commands.h
> @@ -4440,6 +4440,16 @@ struct ec_response_i2c_passthru_protect {
>  
>  #define MAX_CEC_MSG_LEN 16
>  
> +/*
> + * Helper macros for packing/unpacking cec_events.
> + * bits[27:0] : bitmask of events from enum mkbp_cec_event
> + * bits[31:28]: port number
> + */
> +#define EC_MKBP_EVENT_CEC_PACK(events, port) \
> +		(((events) & GENMASK(27, 0)) | (((port) & 0xf) << 28))
> +#define EC_MKBP_EVENT_CEC_GET_EVENTS(event) ((event) & GENMASK(27, 0))
> +#define EC_MKBP_EVENT_CEC_GET_PORT(event) (((event) >> 28) & 0xf)
> +
>  /* CEC message from the AP to be written on the CEC bus */
>  #define EC_CMD_CEC_WRITE_MSG 0x00B8
>