linux-kernel - Re: [PATCH 5/7] PPS: serial clients support.

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Date:	Thu, 20 Mar 2008 13:04:00 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Rodolfo Giometti <giometti@...ux.it>
Cc:	linux-kernel@...r.kernel.org, dwmw2@...radead.org,
	davej@...hat.com, sam@...nborg.org, greg@...ah.com,
	randy.dunlap@...cle.com, giometti@...ux.it
Subject: Re: [PATCH 5/7] PPS: serial clients support.

On Thu,  6 Mar 2008 13:09:04 +0100
Rodolfo Giometti <giometti@...ux.it> wrote:

> Adds support for the PPS sources connected with the CD (Carrier
> Detect) pin of a serial port.
> 
> ...
>
> +#ifdef CONFIG_PPS_CLIENT_UART
> +
> +static int
> +uart_register_pps_port(struct uart_state *state, struct uart_port *port)
> +{
> +	struct tty_driver *drv = port->info->tty->driver;
> +	int ret;
> +
> +	state->pps_info.owner = THIS_MODULE;
> +	state->pps_info.dev = port->dev;
> +	snprintf(state->pps_info.name, PPS_MAX_NAME_LEN, "%s%d",
> +		drv->driver_name, port->line);
> +	snprintf(state->pps_info.path, PPS_MAX_NAME_LEN, "/dev/%s%d",
> +		drv->name, port->line);

umm, why are we hard-wiring "/dev" into the kernel source?  Is it just for
user-friendly printks?

> +	state->pps_info.mode = PPS_CAPTUREBOTH | \
> +			PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
> +			PPS_CANWAIT | PPS_TSFMT_TSPEC;
> +
> +	ret = pps_register_source(&state->pps_info, PPS_CAPTUREBOTH | \
> +				PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
> +	if (ret < 0) {
> +		dev_err(port->dev, "cannot register PPS source \"%s\"\n",
> +						state->pps_info.path);
> +		return ret;
> +	}
> +	port->pps_source = ret;
> +	dev_dbg(port->dev, "PPS source #%d \"%s\" added\n",
> +		port->pps_source, state->pps_info.path);
> +
> +	return 0;
> +}
> +
> +static void
> +uart_unregister_pps_port(struct uart_state *state, struct uart_port *port)
> +{
> +	pps_unregister_source(port->pps_source);
> +	dev_dbg(port->dev, "PPS source #%d \"%s\" removed\n",
> +				port->pps_source, state->pps_info.path);
> +}
> +
> +#else
> +
> +#define uart_register_pps_port(state, port)	do { } while (0)
> +#define uart_unregister_pps_port(state, port)	do { } while (0)

Please never implement in cpp that which can be implemented in C.  These
should have been static inlines.  That's nicer, matches the
CONFIG_PPS_CLIENT_UART=y code and provides type checking.

> +#endif /* CONFIG_PPS_CLIENT_UART */
> +
>  static int uart_set_info(struct uart_state *state,
>  			 struct serial_struct __user *newinfo)
>  {
> @@ -810,11 +859,19 @@ static int uart_set_info(struct uart_state *state,
>  			(port->flags & UPF_LOW_LATENCY) ? 1 : 0;
>  
>   check_and_exit:
> +	/* PPS support enabled/disabled? */
> +	if ((old_flags & UPF_HARDPPS_CD) != (new_flags & UPF_HARDPPS_CD)) {
> +		if (new_flags & UPF_HARDPPS_CD)
> +			uart_register_pps_port(state, port);
> +		else
> +			uart_unregister_pps_port(state, port);
> +	}
> +
>  	retval = 0;
>  	if (port->type == PORT_UNKNOWN)
>  		goto exit;
>  	if (state->info->flags & UIF_INITIALIZED) {
> -		if (((old_flags ^ port->flags) & UPF_SPD_MASK) ||
> +		if (((old_flags ^ port->flags) & (UPF_SPD_MASK|UPF_HARDPPS_CD)) ||
>  		    old_custom_divisor != port->custom_divisor) {
>  			/*
>  			 * If they're setting up a custom divisor or speed,
> @@ -2148,6 +2205,12 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
>  		port->ops->config_port(port, flags);
>  	}
>  
> +	/*
> +	 * Add the PPS support for the current port.
> +	 */
> +	if (port->flags & UPF_HARDPPS_CD)
> +		uart_register_pps_port(state, port);
> +
>  	if (port->type != PORT_UNKNOWN) {
>  		unsigned long flags;
>  
> @@ -2405,6 +2468,12 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
>  	mutex_unlock(&state->mutex);
>  
>  	/*
> +	 * Remove PPS support from the current port.
> +	 */
> +	if (port->flags & UPF_HARDPPS_CD)
> +		uart_unregister_pps_port(state, port);
> +
> +	/*
>  	 * Remove the devices from the tty layer
>  	 */
>  	tty_unregister_device(drv->tty_driver, port->line);

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