cyclic/watchdog patches, v4 #542
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added 3 commits
May 16, 2024 09:21
We are not checking the return value of strdup(), nor freeing the string in cyclic_unregister(). However, all current users either pass a string literal or the dev->name of the client device. So in all cases the name string will live at least as long as the cyclic_info is registered, so just make that a requirement. Reviewed-by: Stefan Roese <sr@denx.de>
Currently, the cyclic_register() done in wdt_start() is not undone in wdt_stop(). Moreover, calling wdt_start multiple times (which is perfectly allowed on an already started device, e.g. to change the timeout value) will result in another struct cyclic_info being registered, referring to the same watchdog device. This can easily be seen on e.g. a wandboard: => cyclic list function: watchdog@20bc000, cpu-time: 22 us, frequency: 1.01 times/s => wdt list watchdog@20bc000 (imx_wdt) => wdt dev watchdog@20bc000 => wdt start 50000 WDT: Started watchdog@20bc000 with servicing every 1000ms (50s timeout) => cyclic list function: watchdog@20bc000, cpu-time: 37 us, frequency: 1.03 times/s function: watchdog@20bc000, cpu-time: 241 us, frequency: 1.01 times/s => wdt start 12345 WDT: Started watchdog@20bc000 with servicing every 1000ms (12s timeout) => cyclic list function: watchdog@20bc000, cpu-time: 36 us, frequency: 1.03 times/s function: watchdog@20bc000, cpu-time: 100 us, frequency: 1.04 times/s function: watchdog@20bc000, cpu-time: 299 us, frequency: 1.00 times/s So properly unregister the watchdog device from the cyclic framework in wdt_stop(). In wdt_start(), we cannot just skip the registration, as the (new) timeout value may mean that we have to ask the cyclic framework to call us more often. So if we're already running, first unregister the old cyclic instance. Reviewed-by: Stefan Roese <sr@denx.de>
…ucture
There are of course not a whole lot of examples in-tree yet, but
before they appear, let's make this API change: Instead of separately
allocating a 'struct cyclic_info', make the users embed such an
instance in their own structure, and make the convention that the
callback simply receives the 'struct cyclic_info *', from which the
clients can get their own data using the container_of() macro.
This has a number of advantages.
First, it means cyclic_register() simply cannot fail, simplifying the
code. The necessary storage will simply be allocated automatically
when the client's own structure is allocated (often via
uclass_priv_auto or similar).
Second, code for which CONFIG_CYCLIC is just an option can more easily
be written without #ifdefs, if we just provide an empty struct
cyclic_info {}. For example, the nested CONFIG_IS_ENABLED()s in
https://lore.kernel.org/u-boot/20240316201416.211480-1-marek.vasut+renesas@mailbox.org/
are mostly due to the existence of the 'struct cyclic_info *' member
being guarded by #ifdef CONFIG_CYCLIC.
And we do probably want to avoid the extra memory overhead of that
member when !CONFIG_CYCLIC. But that is automatic if, instead of a
'struct cyclic_info *', one simply embeds a 'struct cyclic_info',
which will have size 0 when !CONFIG_CYCLIC. Also, the no-op
cyclic_register() function can just unconditionally be called, and the
compiler will see that (1) the callback is referenced, so not emit a
warning for a maybe-unused function and (2) see that it can actually
never be reached, so not emit any code for it.
Reviewed-by: Stefan Roese <sr@denx.de>
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