Messages in this thread | | | Date | Thu, 7 Jul 2011 16:33:35 -0700 | From | Greg KH <> | Subject | Re: [PATCH v3 3/3] char drivers: ramoops debugfs entry |
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On Thu, Jul 07, 2011 at 04:27:27PM -0700, Andrew Morton wrote: > On Thu, 7 Jul 2011 16:16:43 -0700 > Sergiu Iordache <sergiu@google.com> wrote: > > > Ramoops currently dumps the log of a panic/oops in a memory area which > > is known not to be overwritten on restart (for example 1MB starting at > > 15MB). The way it works is by dividing the memory area in records of a > > set size (fixed at 4K before my patches, configurable after) and by > > dumping a record there for each oops/panic. The problem is that right > > now you have to access that memory area through other means, such as > > /dev/mem, which is not always possible. > > > > What my patch did was to add a debugfs entry which returns a valid > > record each time (a single dump done by ramoops). The first call > > returns the first dump. The first call after the last valid dump > > returns an empty buffer. . > > Please fully describe this "record" in the v2 patch changelog. We'll > want to review it for endianness, 32/64-bit compat issues, > maintainability, extensibility, etc. > > > After it has returned nothing, the next > > calls return records from the start again. > > That sounds a bit weird. One would expect it to keep returning zero, > requiring userspace to lseek or close/open. > > > The validity of a dump is > > checked by looking after the header. Any comments on this approach are > > welcome. > > > > Changing the entry from debugfs to sysfs wouldn't be a problem. If > > sysfs is a valid solution I'll come with a patch that updates the > > documentation as well along with the sysfs entry. > > sysfs sounds OK to me. Then again, sysfs is supposed to be > one-value-per-file, so using it would be naughty. > > I dunno, I'd be inclined to abuse the sysfs rule and hope that nobody > notices rather than create a fake char device. But there's certainly > plenty of precedent for the fake char driver.
No, please don't abuse sysfs that way.
Use debugfs or a char device node.
thanks,
greg k-h
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