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Message-ID: <5B8DA87D05A7694D9FA63FD143655C1B540FBDCC@hasmsx108.ger.corp.intel.com>
Date: Wed, 23 Dec 2015 22:48:34 +0000
From: "Winkler, Tomas" <tomas.winkler@...el.com>
To: Guenter Roeck <linux@...ck-us.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Wim Van Sebroeck <wim@...ana.be>
CC: "Usyskin, Alexander" <alexander.usyskin@...el.com>,
"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [char-misc-next v3 4/8] watchdog: mei_wdt: add status debugfs
entry
>
> On 12/21/2015 03:17 PM, Tomas Winkler wrote:
> > Add entry for dumping current watchdog internal state
> >
> > Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
> > ---
> > V2: new in the series
> > V3: rebase
> > drivers/watchdog/mei_wdt.c | 88
> ++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 88 insertions(+)
> >
> > diff --git a/drivers/watchdog/mei_wdt.c b/drivers/watchdog/mei_wdt.c
> > index 5b28a1e95ac1..ab9aec218d69 100644
> > --- a/drivers/watchdog/mei_wdt.c
> > +++ b/drivers/watchdog/mei_wdt.c
> > @@ -15,6 +15,7 @@
> > #include <linux/module.h>
> > #include <linux/slab.h>
> > #include <linux/interrupt.h>
> > +#include <linux/debugfs.h>
> > #include <linux/watchdog.h>
> >
> > #include <linux/uuid.h>
> > @@ -54,6 +55,24 @@ enum mei_wdt_state {
> > MEI_WDT_STOPPING,
> > };
> >
> > +#if IS_ENABLED(CONFIG_DEBUG_FS)
> > +static const char *mei_wdt_state_str(enum mei_wdt_state state)
> > +{
> > + switch (state) {
> > + case MEI_WDT_IDLE:
> > + return "IDLE";
> > + case MEI_WDT_START:
> > + return "START";
> > + case MEI_WDT_RUNNING:
> > + return "RUNNING";
> > + case MEI_WDT_STOPPING:
> > + return "STOPPING";
> > + default:
> > + return "unknown";
> > + }
> > +}
> > +#endif /* CONFIG_DEBUG_FS */
> > +
> I still don't understand why this code has to be here instead of
> further below (at <----> mark).
Once it follow closely after enum definition, second in the next patch the
Ifdef is removed since we use the function in debug output and not only in debugfs.
>
> > struct mei_wdt;
> >
> > /**
> > @@ -76,6 +95,8 @@ struct mei_wdt_dev {
> > * @cldev: mei watchdog client device
> > * @state: watchdog internal state
> > * @timeout: watchdog current timeout
> > + *
> > + * @dbgfs_dir: debugfs dir entry
> > */
> > struct mei_wdt {
> > struct mei_wdt_dev *mwd;
> > @@ -83,6 +104,10 @@ struct mei_wdt {
> > struct mei_cl_device *cldev;
> > enum mei_wdt_state state;
> > u16 timeout;
> > +
> > +#if IS_ENABLED(CONFIG_DEBUG_FS)
> > + struct dentry *dbgfs_dir;
> > +#endif /* CONFIG_DEBUG_FS */
> > };
> >
> > /*
> > @@ -387,6 +412,65 @@ static int mei_wdt_register(struct mei_wdt *wdt)
> > return 0;
> > }
> >
> > +#if IS_ENABLED(CONFIG_DEBUG_FS)
> > +
>
> <---->
>
> > +static ssize_t mei_dbgfs_read_state(struct file *file, char __user *ubuf,
> > + size_t cnt, loff_t *ppos)
> > +{
> > + struct mei_wdt *wdt = file->private_data;
> > + const size_t bufsz = 32;
> > + char buf[32];
> > + ssize_t pos = 0;
> > +
> > + pos += scnprintf(buf + pos, bufsz - pos, "state: %s\n",
> > + mei_wdt_state_str(wdt->state));
> > +
> Seems to me that "pos = ..." would accomplish exactly the same
> without having to pre-initialize pos. I also don't understand the use of
> "+ pos" and "- pos" in the parameter field. pos is 0, isn't it ?
> When would it ever be non-0 ?
>
> pos = scnprintf(buf, sizeof(buf), "state: %s\n", mei_wdt_state_str(wdt-
> >state));
>
> What am I missing here ?
Not you are not missing anything, it's just an idiom taken from all my debugfs function with multiline output.
>
> > + return simple_read_from_buffer(ubuf, cnt, ppos, buf, pos);
> > +}
> > +
> > +static const struct file_operations dbgfs_fops_state = {
> > + .open = simple_open,
> > + .read = mei_dbgfs_read_state,
> > + .llseek = generic_file_llseek,
> > +};
> > +
> > +static void dbgfs_unregister(struct mei_wdt *wdt)
> > +{
> > + if (!wdt->dbgfs_dir)
> > + return;
> > + debugfs_remove_recursive(wdt->dbgfs_dir);
>
> debugfs_remove_recursive() checks if the parameter is NULL,
> so it is not necessary to check if it is NULL before the call.
Correct, I can be fixed.
>
> > + wdt->dbgfs_dir = NULL;
> > +}
> > +
> > +static int dbgfs_register(struct mei_wdt *wdt)
> > +{
> > + struct dentry *dir, *f;
> > +
> > + dir = debugfs_create_dir(KBUILD_MODNAME, NULL);
> > + if (!dir)
> > + return -ENOMEM;
> > +
> > + wdt->dbgfs_dir = dir;
> > + f = debugfs_create_file("state", S_IRUSR, dir, wdt, &dbgfs_fops_state);
> > + if (!f)
> > + goto err;
> > +
> > + return 0;
> > +err:
> > + dbgfs_unregister(wdt);
> > + return -ENODEV;
>
> The error value is ignored by the caller - why bother returning an error in the first
> place ?
A function doesn't take responsibility on how it used.
>
> > +}
> > +
> > +#else
> > +
> > +static inline void dbgfs_unregister(struct mei_wdt *wdt) {}
> > +
> > +static inline int dbgfs_register(struct mei_wdt *wdt)
> > +{
> > + return 0;
> > +}
> > +#endif /* CONFIG_DEBUG_FS */
> > +
> > static int mei_wdt_probe(struct mei_cl_device *cldev,
> > const struct mei_cl_device_id *id)
> > {
> > @@ -414,6 +498,8 @@ static int mei_wdt_probe(struct mei_cl_device *cldev,
> > if (ret)
> > goto err_disable;
> >
> > + dbgfs_register(wdt);
> > +
> > return 0;
> >
> > err_disable:
> > @@ -433,6 +519,8 @@ static int mei_wdt_remove(struct mei_cl_device *cldev)
> >
> > mei_cldev_disable(cldev);
> >
> > + dbgfs_unregister(wdt);
> > +
> > kfree(wdt);
> >
> > return 0;
> >
--
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