linux-kernel - Re: [PATCH v2] pwm: fix pwm-rz-mtu3.c build errors

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Date:   Tue, 18 Jul 2023 18:57:16 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Randy Dunlap <rd.dunlab@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-pwm@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v2] pwm: fix pwm-rz-mtu3.c build errors

On Tue, Jul 18, 2023 at 03:24:58PM +0200, Thierry Reding wrote:
> On Tue, Jul 18, 2023 at 02:05:42PM +0200, Geert Uytterhoeven wrote:
> > Hi Randy,
> > 
> > On Tue, Jul 18, 2023 at 8:44 AM Randy Dunlap <rd.dunlab@...il.com> wrote:
> > > From: Randy Dunlap <rd.dunlab@...il.com>
> > >
> > > When (MFD) RZ_MTU3=m and PWM_RZ_MTU3=y, there are numerous build errors:
> > >
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_config':
> > > drivers/pwm/pwm-rz-mtu3.c:374: undefined reference to `rz_mtu3_disable'
> > > ld: drivers/pwm/pwm-rz-mtu3.c:377: undefined reference to `rz_mtu3_8bit_ch_write'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_write_tgr_registers':
> > > drivers/pwm/pwm-rz-mtu3.c:110: undefined reference to `rz_mtu3_16bit_ch_write'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_config':
> > > drivers/pwm/pwm-rz-mtu3.c:382: undefined reference to `rz_mtu3_8bit_ch_write'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_write_tgr_registers':
> > > drivers/pwm/pwm-rz-mtu3.c:110: undefined reference to `rz_mtu3_16bit_ch_write'
> > > ld: drivers/pwm/pwm-rz-mtu3.c:111: undefined reference to `rz_mtu3_16bit_ch_write'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_config':
> > > drivers/pwm/pwm-rz-mtu3.c:397: undefined reference to `rz_mtu3_enable'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_disable':
> > > drivers/pwm/pwm-rz-mtu3.c:259: undefined reference to `rz_mtu3_8bit_ch_write'
> > > ld: drivers/pwm/pwm-rz-mtu3.c:264: undefined reference to `rz_mtu3_disable'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_enable':
> > > drivers/pwm/pwm-rz-mtu3.c:230: undefined reference to `rz_mtu3_8bit_ch_write'
> > > ld: drivers/pwm/pwm-rz-mtu3.c:234: undefined reference to `rz_mtu3_8bit_ch_write'
> > > ld: drivers/pwm/pwm-rz-mtu3.c:238: undefined reference to `rz_mtu3_enable'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_is_ch_enabled':
> > > drivers/pwm/pwm-rz-mtu3.c:155: undefined reference to `rz_mtu3_is_enabled'
> > > ld: drivers/pwm/pwm-rz-mtu3.c:162: undefined reference to `rz_mtu3_8bit_ch_read'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_read_tgr_registers':
> > > drivers/pwm/pwm-rz-mtu3.c:102: undefined reference to `rz_mtu3_16bit_ch_read'
> > > ld: drivers/pwm/pwm-rz-mtu3.c:102: undefined reference to `rz_mtu3_16bit_ch_read'
> > > ld: drivers/pwm/pwm-rz-mtu3.c:103: undefined reference to `rz_mtu3_16bit_ch_read'
> > > ld: vmlinux.o: in function `rz_mtu3_pwm_get_state':
> > > drivers/pwm/pwm-rz-mtu3.c:296: undefined reference to `rz_mtu3_8bit_ch_read'
> > >
> > > Modify the dependencies of PWM_RZ_MTU3 so that COMPILE_TEST is
> > > still allowed but PWM_RZ_MTU3 depends on RZ_MTU3 if it is being built
> > > but also allow the latter not to be built.
> > >
> > > Fixes: 254d3a727421 ("pwm: Add Renesas RZ/G2L MTU3a PWM driver")
> > > Signed-off-by: Randy Dunlap <rd.dunlab@...il.com
> > 
> > Thanks for your patch!
> > 
> > > --- a/drivers/pwm/Kconfig
> > > +++ b/drivers/pwm/Kconfig
> > > @@ -505,7 +505,8 @@ config PWM_ROCKCHIP
> > >
> > >  config PWM_RZ_MTU3
> > >         tristate "Renesas RZ/G2L MTU3a PWM Timer support"
> > > -       depends on RZ_MTU3 || COMPILE_TEST
> > > +       depends on COMPILE_TEST
> > 
> > This makes the driver always depend on COMPILE_TEST,
> > which is definitely not what we want.
> 
> Honestly, do we really need all of this complexity? I have specific
> configurations to test all of the PWM drivers to make sure they build.
> There's probably edge cases that don't get tested, but sooner or later I
> expect some build bot will encounter those and then we can rectify
> things. But in many cases that I've seen COMPILE_TEST just happens to do
> more harm than good.

Without COMPILE_TEST you'd need to build at least for the following
archs to build all pwm drivers:

	armv4+5
	armv7
	armv7m
	arm64
	mips
	riscv
	shmobile
	x86

I personally like COMPILE_TEST as it reduces the number of needed test
builds to 1 (I think).

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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