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[PATCH] ARM: davinci: only use NVMEM when available

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  [PATCH] ARM: davinci: only use NVMEM when available Arnd Bergmann <arnd@arndb.de> - 2016-03-15 22:40 +0100
    Re: [PATCH] ARM: davinci: only use NVMEM when available Srinivas Kandagatla <srinivas.kandagatla@linaro.org> - 2016-03-17 11:30 +0100
      Re: [PATCH] ARM: davinci: only use NVMEM when available Arnd Bergmann <arnd@arndb.de> - 2016-03-17 11:40 +0100

#1358260 — [PATCH] ARM: davinci: only use NVMEM when available

The davinci platform contains code that calls into the nvmem
subsystem, but that might be a loadable module, causing a
link error:

arch/arm/mach-davinci/built-in.o: In function `davinci_get_mac_addr':
:(.text+0x1088): undefined reference to `nvmem_device_read'
arch/arm/mach-davinci/built-in.o: In function `read_factory_config':
:(.text+0x214c): undefined reference to `nvmem_device_read'

Also, when NVMEM is completely disabled, the functions fail with
nonobvious error messages.

This ensures we only call the API functions when the code is actually
reachable from the board file, and otherwise prints a unique log
message.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: bec3c11bad0e ("misc: at24: replace memory_accessor with nvmem_device_read")
---

Hi Greg,

The commit that introduced this is currently in the char-misc tree,
please apply this fixup on top if you haven't already sent it to Linus.

 arch/arm/mach-davinci/board-mityomapl138.c | 5 +++++
 arch/arm/mach-davinci/common.c             | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/arch/arm/mach-davinci/board-mityomapl138.c b/arch/arm/mach-davinci/board-mityomapl138.c
index d97c588550ad..bc4e63fa9808 100644
--- a/arch/arm/mach-davinci/board-mityomapl138.c
+++ b/arch/arm/mach-davinci/board-mityomapl138.c
@@ -121,6 +121,11 @@ static void read_factory_config(struct nvmem_device *nvmem, void *context)
 	const char *partnum = NULL;
 	struct davinci_soc_info *soc_info = &davinci_soc_info;
 
+	if (!IS_BUILTIN(CONFIG_NVMEM)) {
+		pr_warn("Factory Config not available without CONFIG_NVMEM\n");
+		goto bad_config;
+	}
+
 	ret = nvmem_device_read(nvmem, 0, sizeof(factory_config),
 				&factory_config);
 	if (ret != sizeof(struct factory_config)) {
diff --git a/arch/arm/mach-davinci/common.c b/arch/arm/mach-davinci/common.c
index f55ef2ef2f92..742133b7266a 100644
--- a/arch/arm/mach-davinci/common.c
+++ b/arch/arm/mach-davinci/common.c
@@ -33,6 +33,11 @@ void davinci_get_mac_addr(struct nvmem_device *nvmem, void *context)
 	char *mac_addr = davinci_soc_info.emac_pdata->mac_addr;
 	off_t offset = (off_t)context;
 
+	if (!IS_BUILTIN(CONFIG_NVMEM)) {
+		pr_warn("Cannot read MAC addr from EEPROM without CONFIG_NVMEM\n");
+		return;
+	}
+
 	/* Read MAC addr from EEPROM */
 	if (nvmem_device_read(nvmem, offset, ETH_ALEN, mac_addr) == ETH_ALEN)
 		pr_info("Read MAC addr from EEPROM: %pM\n", mac_addr);
-- 
2.7.0

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#1359712

Thanks for the patch,

On 15/03/16 21:34, Arnd Bergmann wrote:
> The davinci platform contains code that calls into the nvmem
> subsystem, but that might be a loadable module, causing a
> link error:
>
> arch/arm/mach-davinci/built-in.o: In function `davinci_get_mac_addr':
> :(.text+0x1088): undefined reference to `nvmem_device_read'
> arch/arm/mach-davinci/built-in.o: In function `read_factory_config':
> :(.text+0x214c): undefined reference to `nvmem_device_read'
>
This fix does not look correct to me.

IMO, This is a issue with incorrect dependencies in the Kconfig, we 
should not attempt to fix it in the code, rather fix the kconfig 
dependencies in the mach-davnici or the EEPROM_AT24 kconfig itself. one 
of them should select the NVMEM.


thanks,
srini



> Also, when NVMEM is completely disabled, the functions fail with
> nonobvious error messages.
>
> This ensures we only call the API functions when the code is actually
> reachable from the board file, and otherwise prints a unique log
> message.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: bec3c11bad0e ("misc: at24: replace memory_accessor with nvmem_device_read")

> ---
>
> Hi Greg,
>
> The commit that introduced this is currently in the char-misc tree,
> please apply this fixup on top if you haven't already sent it to Linus.
>
>   arch/arm/mach-davinci/board-mityomapl138.c | 5 +++++
>   arch/arm/mach-davinci/common.c             | 5 +++++
>   2 files changed, 10 insertions(+)
>
> diff --git a/arch/arm/mach-davinci/board-mityomapl138.c b/arch/arm/mach-davinci/board-mityomapl138.c
> index d97c588550ad..bc4e63fa9808 100644
> --- a/arch/arm/mach-davinci/board-mityomapl138.c
> +++ b/arch/arm/mach-davinci/board-mityomapl138.c
> @@ -121,6 +121,11 @@ static void read_factory_config(struct nvmem_device *nvmem, void *context)
>   	const char *partnum = NULL;
>   	struct davinci_soc_info *soc_info = &davinci_soc_info;
>
> +	if (!IS_BUILTIN(CONFIG_NVMEM)) {
> +		pr_warn("Factory Config not available without CONFIG_NVMEM\n");
> +		goto bad_config;
> +	}
> +
>   	ret = nvmem_device_read(nvmem, 0, sizeof(factory_config),
>   				&factory_config);
>   	if (ret != sizeof(struct factory_config)) {
> diff --git a/arch/arm/mach-davinci/common.c b/arch/arm/mach-davinci/common.c
> index f55ef2ef2f92..742133b7266a 100644
> --- a/arch/arm/mach-davinci/common.c
> +++ b/arch/arm/mach-davinci/common.c
> @@ -33,6 +33,11 @@ void davinci_get_mac_addr(struct nvmem_device *nvmem, void *context)
>   	char *mac_addr = davinci_soc_info.emac_pdata->mac_addr;
>   	off_t offset = (off_t)context;
>
> +	if (!IS_BUILTIN(CONFIG_NVMEM)) {
> +		pr_warn("Cannot read MAC addr from EEPROM without CONFIG_NVMEM\n");
> +		return;
> +	}
> +
>   	/* Read MAC addr from EEPROM */
>   	if (nvmem_device_read(nvmem, offset, ETH_ALEN, mac_addr) == ETH_ALEN)
>   		pr_info("Read MAC addr from EEPROM: %pM\n", mac_addr);
>

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#1359720

On Thursday 17 March 2016 10:26:28 Srinivas Kandagatla wrote:
> Thanks for the patch,
> 
> On 15/03/16 21:34, Arnd Bergmann wrote:
> > The davinci platform contains code that calls into the nvmem
> > subsystem, but that might be a loadable module, causing a
> > link error:
> >
> > arch/arm/mach-davinci/built-in.o: In function `davinci_get_mac_addr':
> > :(.text+0x1088): undefined reference to `nvmem_device_read'
> > arch/arm/mach-davinci/built-in.o: In function `read_factory_config':
> > :(.text+0x214c): undefined reference to `nvmem_device_read'
> >
> This fix does not look correct to me.
> 
> IMO, This is a issue with incorrect dependencies in the Kconfig, we 
> should not attempt to fix it in the code, rather fix the kconfig 
> dependencies in the mach-davnici or the EEPROM_AT24 kconfig itself. one 
> of them should select the NVMEM.

Those 'select' statements are an endless source of trouble. The code
already builds fine if NVMEM is disabled (falling back to inline
stub calls), or if NVMEM is built-in and AT24 is not present (leading
to the call failing later), and that seems to be a reasonable fallback
for users that really don't want those drivers.

	Arnd

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