From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Likely Subject: Re: [PATCH] dt: add helper functions to read u32 and string property values Date: Sun, 3 Jul 2011 15:03:12 -0600 Message-ID: <20110703210312.GA13742@ponder.secretlab.ca> References: <1309449370-9554-1-git-send-email-thomas.abraham@linaro.org> <20110630181353.GA6674@ponder.secretlab.ca> <20110703035527.GB9742@S2100-06.ap.freescale.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20110703035527.GB9742-+NayF8gZjK2ctlrPMvKcciBecyulp+rMXqFh9Ls21Oc@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Shawn Guo Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, patches-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org List-Id: devicetree@vger.kernel.org On Sun, Jul 03, 2011 at 11:55:28AM +0800, Shawn Guo wrote: > On Thu, Jun 30, 2011 at 12:13:53PM -0600, Grant Likely wrote: > > On Thu, Jun 30, 2011 at 09:26:10PM +0530, Thomas Abraham wrote: > > > Add helper functions to retrive unsigned integer and string property values from > > > properties of a device node. These helper functions can be used to lookup a > > > property in a device node, perform error checking and read the property value. > > > > > > [grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org: Proposal and initial implementation] > > > Signed-off-by: Thomas Abraham > > > > Merged, thanks. Bonus points to anyone who submits patches converting > > existing code to this new api. > > > > g. > > > > > --- > > > drivers/of/base.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > include/linux/of.h | 4 +++ > > > 2 files changed, 63 insertions(+), 0 deletions(-) > > > > > > diff --git a/drivers/of/base.c b/drivers/of/base.c > > > index 632ebae..4823b53 100644 > > > --- a/drivers/of/base.c > > > +++ b/drivers/of/base.c > > > @@ -596,6 +596,65 @@ struct device_node *of_find_node_by_phandle(phandle handle) > > > EXPORT_SYMBOL(of_find_node_by_phandle); > > > > > > /** > > > + * of_property_read_u32 - Find a property in a device node and read the > > > + * 32-bit property value > > > + * @np: device node from which the property value is to be read. > > > + * @propname: name of the property to be searched. > > > + * @out_value: returned value, valid if return value is 0. > > > + * > > > + * Search for a property in a device node and read a 32-bit value from a > > > + * property. Returns -EINVAL, if the property does not exist, -ENODATA, if > > > + * property does not have a value, -EOVERFLOW, if the property data isn't > > > + * large enough, and 0 on success. > > > + * > > > + * The out_value is modified only if a valid u32 value can be decoded. > > > + */ > > > +int of_property_read_u32(struct device_node *np, char *propname, u32 *out_value) > > > +{ > > > + struct property *prop = of_find_property(np, propname, NULL); > > > + > > > + if (!prop) > > > + return -EINVAL; > > > + if (!prop->value) > > > + return -ENODATA; > > > + if (sizeof(*out_value) > prop->length) > > > + return -EOVERFLOW; > > > + *out_value = be32_to_cpup(prop->value); > > > + return 0; > > > +} > > > +EXPORT_SYMBOL_GPL(of_property_read_u32); > > > + > > > +/** > > > + * of_property_read_string - Find a property in a device node and return a > > > + * pointer to the property string value. > > > + * @np: device node from which the property value is to be read. > > > + * @propname: name of the property to be searched. > > > + * @out_string: pointer to a null terminated string, valid only if the return > > > + * value is 0. > > > + * > > > + * Returns a pointer to a null terminated property value string. Returns > > > + * -EINVAL, if the property does not exist, -ENODATA, if property does not have > > > + * a value, -EILSEQ, if the string is not null-terminated within the length of > > > + * the property value, and 0 on success. > > > + * > > > + * The out_string value is modified only if a valid string can be decoded. > > > + */ > > > +int of_property_read_string(struct device_node *np, char *propname, > > > + char **out_string) > > When converting my dt code to use this api, the following type > mismatch warning is being seen in a lot of places. > > 'char **' but argument is of type 'const char **' > > This is because the existing codes usually get string from > of_get_property and assign it to a 'const char *'. > > I'm wondering if we should drop the const during converting or > change the api with const added to out_string to get converting > a little bit easier. Add the const to out_string. It's the right thing to do. Can you craft and post a patch doing so? g.