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Message-ID: <BANLkTik9LXTJ--fRwUBscokWraPwOZnpHA@mail.gmail.com>
Date: Tue, 21 Jun 2011 13:38:03 -0600
From: Grant Likely <grant.likely@...retlab.ca>
To: Mitch Bradley <wmb@...mworks.com>
Cc: patches@...aro.org, netdev@...r.kernel.org,
devicetree-discuss@...ts.ozlabs.org,
Jason Liu <jason.hui@...aro.org>, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
Jeremy Kerr <jeremy.kerr@...onical.com>,
Sascha Hauer <s.hauer@...gutronix.de>,
Shawn Guo <shawn.guo@...escale.com>
Subject: Re: [PATCH 1/3] serial/imx: add device tree support
On Tue, Jun 21, 2011 at 1:35 PM, Mitch Bradley <wmb@...mworks.com> wrote:
> What is the problem with
>
> aliases{
> serial0 = "/uart@...0c000";
> }
>
> Properties in the alias node are supposed to have string values.
?
Not sure I follow. Indeed, properties in the aliases node are string values.
Are you referring to how I was proposing some dtc syntax for
generating the alias strings?
g.
>
>
> On 6/21/2011 9:13 AM, Grant Likely wrote:
>>
>> On Tue, Jun 21, 2011 at 7:55 AM, Shawn Guo<shawn.guo@...escale.com>
>> 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.
>>
>> Thanks Shawn. This is definitely on track. Comments below...
>>
>>>
>>> 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;
>>> + };
>>> +
>>
>> Hmmm. David Gibson had tossed out an idea of automatically generating
>> aliases from labels. It may be time to revisit that idea.
>>
>> David, perhaps using this format for a label should turn it into an
>> alias (prefix label with an asterisk):
>>
>> *thealias: i2c@...40000 { /*...*/ };
>>
>> .... although that approach gets *really* hairy when considering that
>> different boards will want different enumeration. How would one
>> override an automatic alias defined by an included .dts file?
>>
>>> chosen {
>>> bootargs = "console=ttymxc0,115200 root=/dev/mmcblk0p3
>>> rootwait";
>>> };
>>> @@ -47,29 +53,29 @@
>>> reg =<0x70000000 0x40000>;
>>> ranges;
>>>
>>> - uart@...0c000 {
>>> + uart2: uart@...0c000 {
>>> compatible = "fsl,imx51-uart",
>>> "fsl,imx21-uart";
>>> reg =<0x7000c000 0x4000>;
>>> interrupts =<33>;
>>> id =<3>;
>>> - fsl,has-rts-cts;
>>> + fsl,uart-has-rtscts;
>>> };
>>> };
>>>
>>> - uart@...bc000 {
>>> + uart0: uart@...bc000 {
>>> compatible = "fsl,imx51-uart", "fsl,imx21-uart";
>>> reg =<0x73fbc000 0x4000>;
>>> interrupts =<31>;
>>> id =<1>;
>>> - fsl,has-rts-cts;
>>> + fsl,uart-has-rtscts;
>>> };
>>>
>>> - uart@...c0000 {
>>> + uart1: uart@...c0000 {
>>> 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++;
>>> + }
>>
>> Rather than parsing the alias strings everytime, it would probably be
>> better to preprocess all the properties in the aliases node and create
>> a lookup table of alias->node references that can be walked quickly
>> and trivially.
>>
>> Also, when obtaining an enumeration for a device, you'll need to be
>> careful about what number gets returned. If the node doesn't match a
>> given alias, but aliases do exist for other devices of like type, then
>> you need to be careful not to assign a number already assigned to
>> another device via an alias (this of course assumes the driver
>> supports dynamics enumeration, which many drivers will). It would be
>>
>> \> +
>>>
>>> + 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;
>>
>> Personally, it an alias isn't present, then I'd dynamically assign a port
>> id.
>>
>>>
>>> - 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);
>>>
>>> --
>>> Regards,
>>> Shawn
>>>
>>>
>>
>>
>>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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