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    SubjectRe: [PATCH 1/3] serial/imx: add device tree support
    I wonder if it makes sense to create a new device node "/linux-devices" to express a desired mapping from device nodes to /dev entries?  The properties could be the names of device special files and the values the corresponding node phandles.



    On 6/21/2011 3:55 AM, Shawn Guo wrote:
    > Hi Grant,
    >
    > I just gave a try to use aliases node for identify the device index.
    > Please take a look and let me know if it's what you expect.
    >
    > On Sun, Jun 19, 2011 at 03:30:02PM +0800, Shawn Guo wrote:
    > [...]
    >>>>
    >>>> +#ifdef CONFIG_OF
    >>>> +static int serial_imx_probe_dt(struct imx_port *sport,
    >>>> + struct platform_device *pdev)
    >>>> +{
    >>>> + struct device_node *node = pdev->dev.of_node;
    >>>> + const __be32 *line;
    >>>> +
    >>>> + if (!node)
    >>>> + return -ENODEV;
    >>>> +
    >>>> + line = of_get_property(node, "id", NULL);
    >>>> + if (!line)
    >>>> + return -ENODEV;
    >>>> +
    >>>> + sport->port.line = be32_to_cpup(line) - 1;
    >>>
    >>> Hmmm, I really would like to be rid of this. Instead, if uarts must
    >>> be enumerated, the driver should look for a /aliases/uart* property
    >>> that matches the of_node. Doing it that way is already established in
    >>> the OpenFirmware documentation, and it ensures there are no overlaps
    >>> in the global namespace.
    >>>
    >>
    >> I just gave one more try to avoid using 'aliases', and you gave a
    >> 'no' again. Now, I know how hard you are on this. Okay, I start
    >> thinking about your suggestion seriously :)
    >>
    >>> We do need some infrastructure to make that easier though. Would you
    >>> have time to help put that together?
    >>>
    >> Ok, I will give it a try.
    >>
    >
    > diff --git a/arch/arm/boot/dts/imx51-babbage.dts b/arch/arm/boot/dts/imx51-babbage.dts
    > index da0381a..f4a5c3c 100644
    > --- a/arch/arm/boot/dts/imx51-babbage.dts
    > +++ b/arch/arm/boot/dts/imx51-babbage.dts
    > @@ -18,6 +18,12 @@
    > compatible = "fsl,imx51-babbage", "fsl,imx51";
    > interrupt-parent =<&tzic>;
    >
    > + aliases {
    > + serial0 =&uart0;
    > + serial1 =&uart1;
    > + serial2 =&uart2;
    > + };
    > +
    > chosen {
    > bootargs = "console=ttymxc0,115200 root=/dev/mmcblk0p3 rootwait";
    > };
    > @@ -47,29 +53,29 @@
    > reg =<0x70000000 0x40000>;
    > ranges;
    >
    > - uart@7000c000 {
    > + uart2: uart@7000c000 {
    > compatible = "fsl,imx51-uart", "fsl,imx21-uart";
    > reg =<0x7000c000 0x4000>;
    > interrupts =<33>;
    > id =<3>;
    > - fsl,has-rts-cts;
    > + fsl,uart-has-rtscts;
    > };
    > };
    >
    > - uart@73fbc000 {
    > + uart0: uart@73fbc000 {
    > compatible = "fsl,imx51-uart", "fsl,imx21-uart";
    > reg =<0x73fbc000 0x4000>;
    > interrupts =<31>;
    > id =<1>;
    > - fsl,has-rts-cts;
    > + fsl,uart-has-rtscts;
    > };
    >
    > - uart@73fc0000 {
    > + uart1: uart@73fc0000 {
    > compatible = "fsl,imx51-uart", "fsl,imx21-uart";
    > reg =<0x73fc0000 0x4000>;
    > interrupts =<32>;
    > id =<2>;
    > - fsl,has-rts-cts;
    > + fsl,uart-has-rtscts;
    > };
    > };
    >
    > diff --git a/drivers/of/base.c b/drivers/of/base.c
    > index 632ebae..13df5d2 100644
    > --- a/drivers/of/base.c
    > +++ b/drivers/of/base.c
    > @@ -737,6 +737,37 @@ err0:
    > EXPORT_SYMBOL(of_parse_phandles_with_args);
    >
    > /**
    > + * of_get_device_index - Get device index by looking up "aliases" node
    > + * @np: Pointer to device node that asks for device index
    > + * @name: The device alias without index number
    > + *
    > + * Returns the device index if find it, else returns -ENODEV.
    > + */
    > +int of_get_device_index(struct device_node *np, const char *alias)
    > +{
    > + struct device_node *aliases = of_find_node_by_name(NULL, "aliases");
    > + struct property *prop;
    > + char name[32];
    > + int index = 0;
    > +
    > + if (!aliases)
    > + return -ENODEV;
    > +
    > + while (1) {
    > + snprintf(name, sizeof(name), "%s%d", alias, index);
    > + prop = of_find_property(aliases, name, NULL);
    > + if (!prop)
    > + return -ENODEV;
    > + if (np == of_find_node_by_path(prop->value))
    > + break;
    > + index++;
    > + }
    > +
    > + return index;
    > +}
    > +EXPORT_SYMBOL(of_get_device_index);
    > +
    > +/**
    > * prom_add_property - Add a property to a node
    > */
    > int prom_add_property(struct device_node *np, struct property *prop)
    > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
    > index da436e0..852668f 100644
    > --- a/drivers/tty/serial/imx.c
    > +++ b/drivers/tty/serial/imx.c
    > @@ -1271,18 +1271,18 @@ static int serial_imx_probe_dt(struct imx_port *sport,
    > struct device_node *node = pdev->dev.of_node;
    > const struct of_device_id *of_id =
    > of_match_device(imx_uart_dt_ids,&pdev->dev);
    > - const __be32 *line;
    > + int line;
    >
    > if (!node)
    > return -ENODEV;
    >
    > - line = of_get_property(node, "id", NULL);
    > - if (!line)
    > + line = of_get_device_index(node, "serial");
    > + if (IS_ERR_VALUE(line))
    > return -ENODEV;
    >
    > - sport->port.line = be32_to_cpup(line) - 1;
    > + sport->port.line = line;
    >
    > - if (of_get_property(node, "fsl,has-rts-cts", NULL))
    > + if (of_get_property(node, "fsl,uart-has-rtscts", NULL))
    > sport->have_rtscts = 1;
    >
    > if (of_get_property(node, "fsl,irda-mode", NULL))
    > diff --git a/include/linux/of.h b/include/linux/of.h
    > index bfc0ed1..3153752 100644
    > --- a/include/linux/of.h
    > +++ b/include/linux/of.h
    > @@ -213,6 +213,8 @@ extern int of_parse_phandles_with_args(struct device_node *np,
    > const char *list_name, const char *cells_name, int index,
    > struct device_node **out_node, const void **out_args);
    >
    > +extern int of_get_device_index(struct device_node *np, const char *alias);
    > +
    > extern int of_machine_is_compatible(const char *compat);
    >
    > extern int prom_add_property(struct device_node* np, struct property* prop);
    >


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