pr_debug

[Tobin C. Harding]

On Wed, Mar 15, 2017 at 12:12:48PM +0100, Bjørn Mork wrote:
> Alexander Kapshuk <alexander.kapshuk at gmail.com> writes:
> 
> >>> On Wed, Mar 15, 2017 at 10:31 AM, Tobin C. Harding <me at tobin.cc> wrote:
> >>> > why does calling pr_debug() with more than one argument cause a sparse
> >>> > warning?
> >>> >
> >>> > drivers/mmc/core/sdio_io.c:70:9: error: unknown field name in initializer
> >>> >
> >>> > sdio_io.c:70:
> >>> > pr_debug("SDIO: Enabling device %s...\n", sdio_func_id(func));
> ..
> > 'sdio_func_id()' is a macro defined here:
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/linux/mmc/sdio_func.h?id=refs/tags/v4.11-rc2
> > #define sdio_func_id(f) (dev_name(&(f)->dev))
> 
> 
> So the "func" in that debug call contains a 'struct device'.  Any
> reason why the pr_debug() shouldn't be converted to something like
> 
>  dev_dbg(&func->dev, "SDIO: Enabling device...\n");

Good point Bjørn, thanks. And thank you Alexander for your input. I
fear I may have sent you both on a wild goose chase with the example
that I chose. pr_debug() causes a sparse warning in many instances
when the format string includes format specifiers.

/* this is fine */
pr_debug("some info string");   

/* this often causes Sparse warning */
pr_debug("string with specifier: %d", foo); 

A simple example can be seen by adding this function

void foo(const char *baz)
{
	pr_debug("cause Sparse warning - %s\n", baz);
}

To a random driver, and running `make C=2 M=drivers/staging/ks7010`

drivers/staging/ks7010/ks_hostif.c:2702:9: error: unknown field name in initializer

For more examples from the kernel tree, running:
$ make -j9 C=2 M=drivers/staging 2>sparse.out

gives many such cases, for example:

drivers/staging/fbtft/fbtft-core.c:472:17: error: unknown field name in initialize
drivers/staging/media/bcm2048/radio-bcm2048.c:2596:17: error: unknown field name in initializer
drivers/staging/dgnc/dgnc_tty.c:1274:17: error: unknown field name in initializer

Also dev_debug causes the same sparse warning at times, for example:

drivers/staging/comedi/comedi_fops.c:352:17: error: unknown field name in initialize

	if (s->busy) {
		dev_dbg(dev->class_dev,
			"subdevice is busy, cannot resize buffer\n");
		return -EBUSY;
	}

And 2 more example instances of dev_debug:
drivers/staging/comedi/drivers/das16.c:578:25: error: unknown field name in initialize
drivers/staging/dgnc/dgnc_tty.c:1274:17: error: unknown field name in initializer

thanks,
Tobin.