linux/drivers/media/dvb-frontends/si21xx.h
Arnd Bergmann 9b174527e7 [media] Add and use IS_REACHABLE macro
In the media drivers, the v4l2 core knows about all submodules
and calls into them from a common function. However this cannot
work if the modules that get called are loadable and the
core is built-in. In that case we get

drivers/built-in.o: In function `set_type':
drivers/media/v4l2-core/tuner-core.c:301: undefined reference to `tea5767_attach'
drivers/media/v4l2-core/tuner-core.c:307: undefined reference to `tea5761_attach'
drivers/media/v4l2-core/tuner-core.c:349: undefined reference to `tda9887_attach'
drivers/media/v4l2-core/tuner-core.c:405: undefined reference to `xc4000_attach'

This was working previously, until the IS_ENABLED() macro was used
to replace the construct like

 #if defined(CONFIG_DVB_CX24110) || (defined(CONFIG_DVB_CX24110_MODULE) && defined(MODULE))

with the difference that the new code no longer checks whether it is being
built as a loadable module itself.

To fix this, this new patch adds an 'IS_REACHABLE' macro, which evaluates
true in exactly the condition that was used previously. The downside
of this is that this trades an obvious link error for a more subtle
runtime failure, but it is clear that the change that introduced the
link error was unintentional and it seems better to revert it for
now. Also, a similar change was originally created by Trent Piepho
and then reverted by teh change to the IS_ENABLED macro.

Ideally Kconfig would be used to avoid the case of a broken dependency,
or the code restructured in a way to turn around the dependency, but either
way would require much larger changes here.

Fixes: 7b34be71db ("[media] use IS_ENABLED() macro")
See-also: c5dec9fb24 ("V4L/DVB (4751): Fix DBV_FE_CUSTOMISE for card drivers compiled into kernel")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
2015-04-08 15:02:07 -03:00

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812 B
C

#ifndef SI21XX_H
#define SI21XX_H
#include <linux/kconfig.h>
#include <linux/dvb/frontend.h>
#include "dvb_frontend.h"
struct si21xx_config {
/* the demodulator's i2c address */
u8 demod_address;
/* minimum delay before retuning */
int min_delay_ms;
};
#if IS_REACHABLE(CONFIG_DVB_SI21XX)
extern struct dvb_frontend *si21xx_attach(const struct si21xx_config *config,
struct i2c_adapter *i2c);
#else
static inline struct dvb_frontend *si21xx_attach(
const struct si21xx_config *config, struct i2c_adapter *i2c)
{
printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
return NULL;
}
#endif
static inline int si21xx_writeregister(struct dvb_frontend *fe, u8 reg, u8 val)
{
int r = 0;
u8 buf[] = {reg, val};
if (fe->ops.write)
r = fe->ops.write(fe, buf, 2);
return r;
}
#endif