Hi Guenter, Thanks for review. :-) feedback inline below On 21 May 2015 at 17:04, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > On 05/21/2015 01:32 AM, fu.wei@xxxxxxxxxx wrote: >> >> From: Fu Wei <fu.wei@xxxxxxxxxx> >> >> Also update Documentation/watchdog/watchdog-kernel-api.txt to >> introduce: >> (1)the new elements in the watchdog_device and watchdog_ops struct; >> (2)the new API "watchdog_init_timeouts". >> >> Reasons: >> (1)kernel already has two watchdog drivers are using "pretimeout": >> drivers/char/ipmi/ipmi_watchdog.c >> drivers/watchdog/kempld_wdt.c(but the definition is different) >> (2)some other dirvers are going to use this: ARM SBSA Generic Watchdog >> >> Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx> >> --- > > > [ ... ] > >> +extern int watchdog_init_timeouts(struct watchdog_device *wdd, >> + unsigned int pretimeout_parm, >> + unsigned int timeout_parm, >> + void (*update_limits)(struct >> watchdog_device *), >> + struct device *dev); >> >> -The watchdog_init_timeout function allows you to initialize the timeout >> field >> -using the module timeout parameter or by retrieving the timeout-sec >> property from >> -the device tree (if the module timeout parameter is invalid). Best >> practice is >> -to set the default timeout value as timeout value in the watchdog_device >> and >> -then use this function to set the user "preferred" timeout value. >> +The watchdog_init_timeouts function allows you to initialize the >> pretimeout and >> +timeout fields using the module pretimeout and timeout parameter or by >> +retrieving the elements in the timeout-sec property(the first element is >> for >> +timeout, the second one is for pretimeout) from the device tree(if the >> module >> +pretimeout and timeout parameter are invalid). >> +Normally, the pretimeout value will affect the limitation of timeout, and >> it >> +is also hardware related. So you can write a function in your driver to >> update >> +the limitation of timeout, according to the pretimeout value. Then pass >> the >> +function pointer by the update_limits parameter. If you driver doesn't >> +need this adjustment, just pass NULL to the update_limits parameter. > > > You've lost me a bit with the update_limits function. > watchdog_init_timeouts() > is called from the driver. yes, that is the help function which will be called from watchdog driver, like SBSA watchdog driver > Why should the function have to call back into > the > driver to update the parameters which are passed from the driver ? Let me explain this, please correct me if I misunderstand something. According to the concept of "pretimeout" in kernel, the timeout contains the pretimeout, like * Kernel/API: P---------| pretimeout * |-------------------------------T timeout If you set up the value of pretimeout, that means pretimeout <min_timeout < timeout < max_timeout < (pretimeout + max_timeout_for_1th_stage) For min_timeout > pretimeout. if some one setup a timeout like : pretimeout > timeout > min_timeout, I think that could be a problem For max_timeout < (pretimeout + max_timeout_for_1th_stage), if some one setup a timeout like (pretimeout + max_timeout_for_1th_stage) < timeout > max_timeout . I have explained a little in doc, but the adjustment may have something to do with hardware, like max_timeout_for_1th_stage(in SBSA watchdog , limited by WCV) maybe this problem wouldn't happen ,if you set up max_timeout to a small number. so you can pass NULL to the pointer. but I think maybe for other device , that may happen. > Seems to me the driver can do that calculation first, then call > watchdog_init_timeouts() with the result. Am I missing something ? maybe I am overthinking it :-) please correct me > > Thanks, > Guenter > -- Best regards, Fu Wei Software Engineer Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch Ph: +86 21 61221326(direct) Ph: +86 186 2020 4684 (mobile) Room 1512, Regus One Corporate Avenue,Level 15, One Corporate Avenue,222 Hubin Road,Huangpu District, Shanghai,China 200021 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
