Re: [PATCH] watchdog device drivers:pc87413_wdt: Rewriting of pc87413_wdt driver to utilize common watchdog interface

[Guenter Roeck <linux@roeck-us.net>]

On Mon, Jul 29, 2019 at 02:20:16PM -0700, Mark Balantzyan wrote:
> There is a potential for the variable swc_base_addr in the call chain of the
> driver initialization function (init) to be used before initialization. This
> brought up the need for, by rewriting the driver to use the common watchdog
> interface, ensuring to have all resources in place. This patch addresses this
> need by rewriting into common watchdog interface utilization for the driver.
> 
> Signed-off-by: Mark Balantzyan <mbalant3@gmail.com>
> 

This patch shows up as corrupted if I try to apply it.

> ---
>  drivers/media/pci/tw686x/Kconfig |  1 +
>  drivers/watchdog/pc87413_wdt.c   | 92 +++++++++++++++-----------------
>  2 files changed, 45 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/media/pci/tw686x/Kconfig
> b/drivers/media/pci/tw686x/Kconfig
> index da8bfee7..079d7464 100644
> --- a/drivers/media/pci/tw686x/Kconfig
> +++ b/drivers/media/pci/tw686x/Kconfig
> @@ -5,6 +5,7 @@ config VIDEO_TW686X
>  	select VIDEOBUF2_DMA_CONTIG
>  	select VIDEOBUF2_DMA_SG
>  	select SND_PCM
> +	select WATCHDOG_CORE
>  	help
>  	  Support for Intersil/Techwell TW686x-based frame grabber cards.
> 
> diff --git a/drivers/watchdog/pc87413_wdt.c b/drivers/watchdog/pc87413_wdt.c
> index 06a892e3..4c330ee5 100644
> --- a/drivers/watchdog/pc87413_wdt.c
> +++ b/drivers/watchdog/pc87413_wdt.c
> @@ -22,12 +22,10 @@
> 
>  #include <linux/module.h>
>  #include <linux/types.h>
> -#include <linux/miscdevice.h>
>  #include <linux/watchdog.h>
>  #include <linux/ioport.h>
>  #include <linux/delay.h>
>  #include <linux/notifier.h>
> -#include <linux/fs.h>
>  #include <linux/reboot.h>
>  #include <linux/init.h>
>  #include <linux/spinlock.h>
> @@ -65,7 +63,6 @@ static char expect_close;		/* is the close expected? */
> 
>  static DEFINE_SPINLOCK(io_lock);	/* to guard us from io races */
> 
> -static bool nowayout = WATCHDOG_NOWAYOUT;
> 
>  /* -- Low level function ----------------------------------------*/
> 
> @@ -216,9 +213,9 @@ static inline void pc87413_disable_sw_wd_trg(void)
> 
>  /* -- Higher level functions ------------------------------------*/
> 
> -/* Enable the watchdog */
> +/* Enable/start the watchdog */
> 
> -static void pc87413_enable(void)
> +static void pc87413_start(void)
>  {
>  	spin_lock(&io_lock);
> 
> @@ -231,9 +228,9 @@ static void pc87413_enable(void)
>  	spin_unlock(&io_lock);
>  }
> 
> -/* Disable the watchdog */
> +/* Disable/stop the watchdog */
> 
> -static void pc87413_disable(void)
> +static void pc87413_stop(void)
>  {
>  	spin_lock(&io_lock);

Locking is handled by the watchdog core. Local locking is no
longer needed.

> 
> @@ -245,9 +242,9 @@ static void pc87413_disable(void)
>  	spin_unlock(&io_lock);
>  }
> 
> -/* Refresh the watchdog */
> +/* Refresh/keepalive the watchdog */
> 
> -static void pc87413_refresh(void)
> +static void pc87413_keepalive(struct watchdog_device *wdd)
>  {
>  	spin_lock(&io_lock);
> 
> @@ -260,6 +257,8 @@ static void pc87413_refresh(void)
>  	pc87413_enable_sw_wd_trg();
> 
>  	spin_unlock(&io_lock);
> +
> +	return 0;
>  }
> 
>  /* -- File operations -------------------------------------------*/
> @@ -278,9 +277,6 @@ static int pc87413_open(struct inode *inode, struct file
> *file)

WHy is this function still there ?

>  	if (test_and_set_bit(0, &timer_enabled))
>  		return -EBUSY;
> 
> -	if (nowayout)
> -		__module_get(THIS_MODULE);
> -
>  	/* Reload and activate timer */
>  	pc87413_refresh();
> 
> @@ -331,7 +327,6 @@ static int pc87413_status(void)
> 
>  /**
>   *	pc87413_write:
> - *	@file: file handle to the watchdog
>   *	@data: data buffer to write
>   *	@len: length in bytes
>   *	@ppos: pointer to the position to write. No seeks allowed
> @@ -345,26 +340,25 @@ static ssize_t pc87413_write(struct file *file, const
> char __user *data,
>  {

This function is no longer needed or used.

>  	/* See if we got the magic character 'V' and reload the timer */
>  	if (len) {
> -		if (!nowayout) {
> -			size_t i;
> -
> -			/* reset expect flag */
> -			expect_close = 0;
> -
> -			/* scan to see whether or not we got the
> -			   magic character */
> -			for (i = 0; i != len; i++) {
> -				char c;
> -				if (get_user(c, data + i))
> -					return -EFAULT;
> -				if (c == 'V')
> -					expect_close = 42;
> -			}
> +		size_t i;
> +
> +		/* reset expect flag */
> +		expect_close = 0;
> +
> +		/* scan to see whether or not we got the
> +		   magic character */
> +		for (i = 0; i != len; i++) {
> +			char c;
> +			if (get_user(c, data + i))
> +				return -EFAULT;
> +			if (c == 'V')
> +				expect_close = 42;
>  		}
> +	}
> 
>  		/* someone wrote to us, we should reload the timer */
> -		pc87413_refresh();
> -	}
> +	pc87413_refresh();
> +
>  	return len;
>  }
> 
> @@ -417,7 +411,7 @@ static long pc87413_ioctl(struct file *file, unsigned int
> cmd,

Another function that is no longer needed. And the above looks corrupted.

>  			retval = 0;
>  		}
>  		if (options & WDIOS_ENABLECARD) {
> -			pc87413_enable();
> +			pc87413_start();
>  			retval = 0;
>  		}
>  		return retval;
> @@ -466,31 +460,32 @@ static int pc87413_notify_sys(struct notifier_block
> *this,

Drivers using the watchdog core should use the watchdog core's
restart notifier.

>  {
>  	if (code == SYS_DOWN || code == SYS_HALT)
>  		/* Turn the card off */
> -		pc87413_disable();
> +		pc87413_stop();
>  	return NOTIFY_DONE;
>  }
> 
>  /* -- Module's structures ---------------------------------------*/
> 
> -static const struct file_operations pc87413_fops = {
> -	.owner		= THIS_MODULE,
> -	.llseek		= no_llseek,
> -	.write		= pc87413_write,
> -	.unlocked_ioctl	= pc87413_ioctl,
> -	.open		= pc87413_open,
> -	.release	= pc87413_release,
> -};
> 
> -static struct notifier_block pc87413_notifier = {
> +static struct notifier_block pc87413wdt_notifier = {
>  	.notifier_call  = pc87413_notify_sys,
>  };
> 
> -static struct miscdevice pc87413_miscdev = {
> -	.minor          = WATCHDOG_MINOR,
> -	.name           = "watchdog",
> -	.fops           = &pc87413_fops,
> +static struct watchdog_ops pc87413wdt_ops = {
> +       .owner = THIS_MODULE,
> +       .start = pc87413wdt_start,
> +       .stop = pc87413wdt_stop,
> +       .ping = pc87413wdt_keepalive,
> +       .set_timeout = pc87413wdt_set_heartbeat,
> +};
> +
> +static struct watchdog_device pc87413wdt_wdd = {
> +       	.info = &pc87413wdt_ident,
> +       	.ops = &pc87413wdt_ops,
> +	.status = WATCHDOG_NOWAYOUT_INIT_STATUS
>  };
> 
> +
>  /* -- Module init functions -------------------------------------*/
> 
>  /**
> @@ -515,7 +510,7 @@ static int __init pc87413_init(void)
>  	if (ret != 0)
>  		pr_err("cannot register reboot notifier (err=%d)\n", ret);
> 
> -	ret = misc_register(&pc87413_miscdev);
> +	ret = watchdog_register_device(&pc87413wdt_wdd);
>  	if (ret != 0) {
>  		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
>  		       WATCHDOG_MINOR, ret);
> @@ -533,13 +528,14 @@ static int __init pc87413_init(void)
>  		goto misc_unreg;
>  	}
> 
> -	pc87413_enable();
> +	pc87413_start();
> 
Hmm ... I don't think starting the watchdog in the probe function is a good
idea. One reason to believe that no one is actually using it.

>  	release_region(io, 2);
> +	pc87413_keepalive(&pc87413wdt_wdd);
>  	return 0;
> 
>  misc_unreg:
> -	misc_deregister(&pc87413_miscdev);
> +	watchdog_unregister_device(&pc87413wdt_wdd)
>  reboot_unreg:
>  	unregister_reboot_notifier(&pc87413_notifier);
>  	release_region(io, 2);

Are you sure you even compiled this file ? It still calls
misc_deregister() in the exit function, but miscdevice.h is
no longer included. And the now unnecessary but still present
functions should at the very least trigger a build warning.

Overall, I don't think you have this hardware. If you do, please provide
logs showing that the new driver is working. Otherwise, I really think it
would be better to leave it alone.

Thanks,
Guenter