Re: [PATCH 2/2] spi: add statistics gathering and reporting methods

[Jakub Kiciński <moorray3@xxxxx>]

On Mon, 4 May 2015 16:25:01 +0200, Martin Sperl wrote:
> > On 04.05.2015, at 15:42, Mark Brown <broonie@xxxxxxxxxx> wrote:
> > This is unsuitable for sysfs as it is, sysfs is strictly one value per
> > file.  debugfs would be a more suitable place for a file like this, or
> > if they are going to go into sysfs they should go in as a directory of
> > files with one value per file like the network device statistics
> > directory.  I'm ambivalent about which is the best place, both have
> > their merits.  
>
> that makes it much more complicated to add things per spi_master
> implementation (which was my original idea: have a framework that exposes
> the distinct transfer modes of the spi-bcm2835 driver (polling, interrupt
> and dma driven) and also to get some stats on how often we run into those
> “corner” cases - that is also why I want to gather the histogram
> statistics, as it may make it easier to understand the use cases of people
> who complain about “performance” in case they share those infos…

You can also consider adding few strategically placed tracepoints.  
It saves the amount of kernel code necessary and is generally more
flexible.
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