linux/drivers/media/dvb-frontends/ix2505v.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

65 lines
1.8 KiB
C

/**
* Driver for Sharp IX2505V (marked B0017) DVB-S silicon tuner
*
* Copyright (C) 2010 Malcolm Priestley
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License Version 2, as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef DVB_IX2505V_H
#define DVB_IX2505V_H
#include <linux/kconfig.h>
#include <linux/i2c.h>
#include "dvb_frontend.h"
/**
* Attach a ix2505v tuner to the supplied frontend structure.
*
* @param fe Frontend to attach to.
* @param config ix2505v_config structure
* @return FE pointer on success, NULL on failure.
*/
struct ix2505v_config {
u8 tuner_address;
/*Baseband AMP gain control 0/1=0dB(default) 2=-2bB 3=-4dB */
u8 tuner_gain;
/*Charge pump output +/- 0=120 1=260 2=555 3=1200(default) */
u8 tuner_chargepump;
/* delay after tune */
int min_delay_ms;
/* disables reads*/
u8 tuner_write_only;
};
#if IS_REACHABLE(CONFIG_DVB_IX2505V)
extern struct dvb_frontend *ix2505v_attach(struct dvb_frontend *fe,
const struct ix2505v_config *config, struct i2c_adapter *i2c);
#else
static inline struct dvb_frontend *ix2505v_attach(struct dvb_frontend *fe,
const struct ix2505v_config *config, struct i2c_adapter *i2c)
{
printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
return NULL;
}
#endif
#endif /* DVB_IX2505V_H */