From mboxrd@z Thu Jan 1 00:00:00 1970 From: "AKASHI, Takahiro" Subject: Re: [PATCH v15 06/16] of/fdt: add helper functions for handling properties Date: Tue, 9 Oct 2018 09:37:37 +0900 Message-ID: <20181009003733.GN32578@linaro.org> References: <20180928064841.14117-1-takahiro.akashi@linaro.org> <20180928064841.14117-7-takahiro.akashi@linaro.org> <20181005030849.GK32578@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring Cc: David Gibson , Catalin Marinas , Will Deacon , David Howells , Vivek Goyal , Herbert Xu , David Miller , dyoung@redhat.com, Baoquan He , Arnd Bergmann , Martin Schwidefsky , Heiko Carstens , prudo@linux.ibm.com, Ard Biesheuvel , James Morse , bhsharma@redhat.com, kexec@lists.infradead.org, "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" , "linux-kernel@vger.kernel.org" , Frank Rowand List-Id: devicetree@vger.kernel.org On Fri, Oct 05, 2018 at 08:23:57AM -0500, Rob Herring wrote: > On Thu, Oct 4, 2018 at 10:07 PM AKASHI, Takahiro > wrote: > > > > Rob, > > > > # I haven't replied to this comment yet. > > > > On Fri, Sep 28, 2018 at 08:44:42AM -0500, Rob Herring wrote: > > > +David Gibson > > > > > > On Fri, Sep 28, 2018 at 1:48 AM AKASHI Takahiro > > > wrote: > > > > > > > > These functions will be used later to handle kexec-specific properties > > > > in arm64's kexec_file implementation. > > > > > > > > Signed-off-by: AKASHI Takahiro > > > > Cc: Rob Herring > > > > Cc: Frank Rowand > > > > Cc: devicetree@vger.kernel.org > > > > --- > > > > drivers/of/fdt.c | 56 ++++++++++++++++++++++++++++++++++++++++++ > > > > include/linux/of_fdt.h | 4 +++ > > > > 2 files changed, 60 insertions(+) > > > > > > > > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c > > > > index 800ad252cf9c..c65c31562ccb 100644 > > > > --- a/drivers/of/fdt.c > > > > +++ b/drivers/of/fdt.c > > > > @@ -25,6 +25,7 @@ > > > > #include > > > > #include > > > > #include > > > > +#include > > > > > > > > #include /* for COMMAND_LINE_SIZE */ > > > > #include > > > > @@ -1323,3 +1324,58 @@ late_initcall(of_fdt_raw_init); > > > > #endif > > > > > > > > #endif /* CONFIG_OF_EARLY_FLATTREE */ > > > > + > > > > +#define FDT_ALIGN(x, a) (((x) + (a) - 1) & ~((a) - 1)) > > > > +#define FDT_TAGALIGN(x) (FDT_ALIGN((x), FDT_TAGSIZE)) > > > > + > > > > +int fdt_prop_len(const char *prop_name, int len) > > > > +{ > > > > + return (strlen(prop_name) + 1) + > > > > + sizeof(struct fdt_property) + > > > > + FDT_TAGALIGN(len); > > > > > > Looks like you are using this to calculate how much space you need to > > > allocate in addition to the current DTB for a couple of new or > > > replaced properties. I'm not sure that this calculation is completely > > > accurate. And it is strange there doesn't seem to be any libfdt > > > function for this already. It would be simpler to just add some fixed > > > additional amount. > > > > > > Maybe David G has comments on this? > > > > > > > +} > > > > + > > > > > > The rest of this should go in drivers/of/fdt_address.c. Ultimately, it > > > should go into libfdt, but I'm fine with having it in the kernel for > > > now. > > > > I'd like to have this function in the kernel for now. > > > > > > +static void fill_property(void *buf, u64 val64, int cells) > > > > +{ > > > > + __be32 val32; > > > > + > > > > + while (cells) { > > > > + val32 = cpu_to_fdt32((val64 >> (32 * (--cells))) & U32_MAX); > > > > + memcpy(buf, &val32, sizeof(val32)); > > > > + buf += sizeof(val32); > > > > > > This is kind of hard to read. I would copy u-boot's fdt_pack_reg function. > > > > Are you sure? > > I originally implemented this function in a similar way that fdt_pack_reg() > > was, but, you suggested, in your past comment[1], that we'd be better to > > have of_read_number()-like implementation. > > > > [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-May/579118.html > > Yeah, you're right. Plus, I'm not sure the u-boot one would work for > unaligned accesses with armv5 and earlier h/w. > > My only comment then is I think you can drop the U32_MAX masking. Okay, then I will leave this function, yet renaming it to cpu64_to_fdt_cells() after Frank's comment. Thanks, -Takahiro Akashi > > Rob