From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Looijmans Subject: Re: [PATCH] [net] nvmem: disallow modular CONFIG_NVMEM Date: Wed, 4 Apr 2018 15:32:43 +0200 Message-ID: <23fe2eeb-127e-7917-0d56-714414cc8c06@topic.nl> References: <20180404103900.4090118-1-arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8BIT Cc: Florian Fainelli , Andrew Lunn , "David S . Miller" , , "Greg Kroah-Hartman" , Oleksij Rempel , Martin Blumenstingl , To: Arnd Bergmann , Srinivas Kandagatla Return-path: In-Reply-To: <20180404103900.4090118-1-arnd@arndb.de> Content-Language: nl Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org For making things build again: Acked-by: Mike Looijmans I'd be interested in use-cases for having nvmem as a module, I cannot think of any. I am working on splitting of_get_nvmem_mac_address(), by moving most of its burden to the nvmem interface. Intend to create this "just give me my bytes" function in nvmem: int of_nvmem_cell_read(struct device_node *np, const char *name, void *buf, size_t bytes); With that in place, of_get_nvmem_mac_address becomes a one-liner: return of_nvmem_cell_read(np, "mac-address", addr, ETH_ALEN); That would allow of_get_nvmem_mac_address to be inlined, and this would move the link issues into modules that actually use that function. Which may still be very confusing, since it means that CONFIG_MACB=y with CONFIG_NVMEM=m will fail, but setting both to "y" or both to "m" will work. So that would introduce more build failures again, right? -- Mike. On 04-04-18 12:38, Arnd Bergmann wrote: > The new of_get_nvmem_mac_address() helper function causes a link error > with CONFIG_NVMEM=m: > > drivers/of/of_net.o: In function `of_get_nvmem_mac_address': > of_net.c:(.text+0x168): undefined reference to `of_nvmem_cell_get' > of_net.c:(.text+0x19c): undefined reference to `nvmem_cell_read' > of_net.c:(.text+0x1a8): undefined reference to `nvmem_cell_put' > > I could not come up with a good solution for this, as the code is always > built-in. Using an #if IS_REACHABLE() check around it would solve the > link time issue but then stop it from working in that configuration. > Making of_nvmem_cell_get() an inline function could also solve that, but > seems a bit ugly since it's somewhat larger than most inline functions, > and it would just bring that problem into the callers. Splitting the > function into a separate file might be an alternative. > > This uses the big hammer by making CONFIG_NVMEM itself a 'bool' symbol, > which avoids the problem entirely but makes the vmlinux larger for anyone > that might use NVMEM support but doesn't need it built-in otherwise. > > Fixes: 9217e566bdee ("of_net: Implement of_get_nvmem_mac_address helper") > Cc: Mike Looijmans > Cc: Florian Fainelli > Cc: Andrew Lunn > Cc: David S. Miller > Cc: netdev@vger.kernel.org > Signed-off-by: Arnd Bergmann > --- > The problem arrived through the networking tree, but it's now in > mainline, so the fix could go through either tree > --- > drivers/nvmem/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig > index 5f9bc787d634..1090924efdb1 100644 > --- a/drivers/nvmem/Kconfig > +++ b/drivers/nvmem/Kconfig > @@ -1,5 +1,5 @@ > menuconfig NVMEM > - tristate "NVMEM Support" > + bool "NVMEM Support" > help > Support for NVMEM(Non Volatile Memory) devices like EEPROM, EFUSES... > > Kind regards, Mike Looijmans System Expert TOPIC Products Materiaalweg 4, NL-5681 RJ Best Postbus 440, NL-5680 AK Best Telefoon: +31 (0) 499 33 69 79 E-mail: mike.looijmans@topicproducts.com Website: www.topicproducts.com Please consider the environment before printing this e-mail