Messages in this thread | | | Subject | Re: [char-misc-next v3 4/8] watchdog: mei_wdt: add status debugfs entry | From | Guenter Roeck <> | Date | Wed, 23 Dec 2015 16:25:52 -0800 |
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On 12/23/2015 02:48 PM, Winkler, Tomas wrote: >> >> 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@intel.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.
I don't think that is a good reason for using the more complex code here.
>> >>> + 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.
For an exported function I would agree, but not in a static function.
Thanks, Guenter
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