linux-kernel - Re: [PATCH v4 3/5] watchdog: ts4800: add driver for TS-4800 watchdog

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Date:	Mon, 23 Nov 2015 18:32:15 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Damien Riegel <damien.riegel@...oirfairelinux.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-watchdog@...r.kernel.org
Cc:	Lee Jones <lee.jones@...aro.org>, robh+dt@...nel.org,
	shawnguo@...nel.org, kernel@...gutronix.de, wim@...ana.be,
	sameo@...ux.intel.com, dinh.linux@...il.com,
	Arnd Bergmann <arnd@...db.de>, kernel@...oirfairelinux.com
Subject: Re: [PATCH v4 3/5] watchdog: ts4800: add driver for TS-4800 watchdog

Hi Damien,

On 11/23/2015 07:17 AM, Damien Riegel wrote:
> This watchdog is instantiated in a FPGA that is memory mapped. It is
> made of only one register, called the feed register. Writing to this
> register will re-arm the watchdog for a given time (and enable it if it
> was disable). It can be disabled by writing a special value into it.
>
> It is part of a syscon block, and the watchdog register offset in this
> block varies from board to board. This offset is passed in the syscon
> property after the phandle to the syscon node.
>
> Signed-off-by: Damien Riegel <damien.riegel@...oirfairelinux.com>
> ---

[ ... ]

> +
> +static int ts4800_wdt_set_timeout(struct watchdog_device *wdd,
> +				  unsigned int timeout)
> +{
> +	struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
> +	int i;
> +
> +	for (i = 0; i <= MAX_TIMEOUT_INDEX; i++) {
> +		if (ts4800_wdt_map[i].timeout >= timeout)
> +			break;
> +	}

If the loop does not break, i will have a value of MAX_TIMEOUT_INDEX + 1,
or 2, pointing after the end of the table. That should never happen,
but still ...

I preferred the earlier version, where you had an extra function.
Only my suggestion was to have that function return MAX_TIMEOUT_INDEX
instead of an error. Alternatively, the check above needs to be
"i < MAX_TIMEOUT_INDEX".

Guenter

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