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SubjectRe: [RFC PATCH 2/2] HISI LPC: Add PNP device support
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On 20/04/2018 13:50, Andy Shevchenko wrote:
> On Fri, 2018-04-20 at 18:07 +0800, John Garry wrote:
>> Currently the driver creates an per-ACPI device mfd_cell
>> for child devices. This does not suit devices which are
>> PNP-compatible, as we expect PNP-compatible devices to
>> derive PNP devices.
>>
>> To add PNP device support, we continue to allow the PNP
>> scan code to create the PNP device (which have the
>> enumeration_by_parent flag set), but expect the PNP
>> scan to defer adding the device to allow the host probe
>> code to do this. In addition, no longer do we create an
>> mfd_cell (platform_device) for PNP-compatible devices.
>>
>> We take this approach so that host probe code can
>> translate the IO resources of the PNP device prior
>> to adding the device.
>

Hi Andy,

Thanks for checking this.

>> + list_for_each_entry(child, &adev->children, node) {
>> + if (acpi_is_pnp_device(child))
>> + continue;
>
> This is good candidate for a separate helper macro
>
> #define for_each_acpi_non_pnp_device(child, adev) \
> ...

Right, I did consider this, but was holding off refining until I get
past RFC stage. In fact, we could also process each child entry in one
loop, like this:

list_for_each_entry(child, &adev->children, node) {
if (acpi_is_pnp_device(child)) {
/* Do PNP compatible device work */

} else {
/* otherwise, make an MFD cell ... */
}

>
> (see, for example, for_each_pci_bridge() implementation as an example)
>
>
>> + list_for_each_entry(child, &adev->children, node) {
>
>> + if (!acpi_is_pnp_device(child))
>> + continue;
>
> Ditto.
>

ok

>> + /*
>> + * Prior to adding the device, we need to translate
>> the
>> + * resources to logical PIO addresses.
>> + */
>> + list_for_each_entry(pnp_res, &pnp_dev->resources,
>> list) {
>> + struct resource *res = &pnp_res->res;
>> +
>
>> + if (res->flags | IORESOURCE_IO)
>
> What does this mean?

Here we check the resource flag for each resource for this PNP device -
for IO resources we must translate the resource value from the bus
address to the logical PIO address.

>
>> + hisi_lpc_acpi_xlat_io_res(child,
>> adev, res);
>> + }
>

Regards,
John


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