From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Gibson Date: Thu, 30 Jun 2016 15:08:57 +1000 Subject: [U-Boot] [PATCH v3 10/12] libfdt: Add overlay application function In-Reply-To: <5774854E.2020008@gmail.com> References: <20160624142757.32735-1-maxime.ripard@free-electrons.com> <20160624142757.32735-11-maxime.ripard@free-electrons.com> <20160627052607.GK4242@voom.fritz.box> <20160627114000.GV4000@lukather> <20160628031252.GZ4242@voom.fritz.box> <5774854E.2020008@gmail.com> Message-ID: <20160630050857.GR8885@voom.fritz.box> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Wed, Jun 29, 2016 at 07:34:54PM -0700, Frank Rowand wrote: > On 06/27/16 20:12, David Gibson wrote: > > On Mon, Jun 27, 2016 at 01:40:00PM +0200, Maxime Ripard wrote: > >> Hi David, > >> > >> On Mon, Jun 27, 2016 at 03:26:07PM +1000, David Gibson wrote: > >>>> +static uint32_t overlay_get_target_phandle(const void *fdto, int fragment) > >>>> +{ > >>>> + const uint32_t *val; > >>>> + int len; > >>>> + > >>>> + val = fdt_getprop(fdto, fragment, "target", &len); > >>>> + if (!val || (*val == 0xffffffff) || (len != sizeof(*val))) > >>>> + return 0; > >>> > >>> This doesn't distinguish between a missing property (which may > >>> indicate a valid overlay using a target-path or some other method) > >>> and a badly formatted 'target' property, which is definitely an error > >>> in the overlay. > >>> > >>> I think those should be treated differently. > >> > >> AFAIK, phandles can have any 32 bits values but 0xffffffff. In order > >> to cover the two cases, we would need to have some error code, but > >> that doesn't really work with returning a uint32_t. > > > > Actually phandles can have any value except 0xffffffff *or* 0. So you > > can use 0 for "couldn't find" and -1 for "badly formatted". > > < snip > > > Hi David, > > I would like to capture this for the specification. > > It seems like I could say that a value of 0 in the FDT is not allowed. > > Then thinking of what Pantelis is doing with overlays, it seems like a > value of 0xffffffff is allowed in the FDT, but it means not a valid > phandle, so do not try to de-reference it. > > Does that sound good? That should be ok. Basically both 0 and -1 are invalid phandle values, so it's up to us if we want to assign them specific "error" meanings. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: not available URL: