Re: [PATCH v1 1/2] platform/x86/intel: Introduce Intel Elkhart Lake PSE I/O

Andy Shevchenko
2025-10-29T08:36:25Z

On Wed, Oct 29, 2025 at 11:50:49AM +0530, Raag Jadav wrote:
> Intel Elkhart Lake Programmable Service Engine (PSE) includes two PCI
> devices that expose two different capabilities of GPIO and Timed I/O
> as a single PCI function through shared MMIO with below layout.
>
> GPIO: 0x0000 - 0x1000
> TIO: 0x1000 - 0x2000
>
> This driver enumerates the PCI parent device and creates auxiliary child
> devices for these capabilities. The actual functionalities are provided
> by their respective auxiliary drivers.

...

> +#include <linux/auxiliary_bus.h>
> +#include <linux/dev_printk.h>
> +#include <linux/device/devres.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/gfp_types.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/sizes.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>

> +#define EHL_PSE_IO_DEV_OFFSET SZ_4K
> +#define EHL_PSE_IO_DEV_SIZE SZ_4K

Not sure if SZ_4K is a good idea for the _OFFSET, the _SIZE is fine. Also why
do we need two? If the devices are of the same size, we don't need to have a
separate offset.

...

> +static int ehl_pse_io_dev_add(struct pci_dev *pci, const char *name, int idx)
> +{
> + struct auxiliary_device *aux_dev;
> + struct device *dev = &pci->dev;
> + struct ehl_pse_io_dev *io_dev;
> + resource_size_t start;
> + int ret;
> +
> + io_dev = kzalloc(sizeof(*io_dev), GFP_KERNEL);
> + if (!io_dev)
> + return -ENOMEM;

Why devm_kzalloc() can't be used? I don't see if the device lifetime is anyhow
different to this object. Am I wrong?

> + start = pci_resource_start(pci, 0);
> + io_dev->irq = pci_irq_vector(pci, idx);
> + io_dev->mem = DEFINE_RES_MEM(start + (EHL_PSE_IO_DEV_OFFSET * idx), EHL_PSE_IO_DEV_SIZE);
> +
> + aux_dev = &io_dev->aux_dev;
> + aux_dev->name = name;
> + aux_dev->id = (pci_domain_nr(pci->bus) << 16) | pci_dev_id(pci);
> + aux_dev->dev.parent = dev;
> + aux_dev->dev.release = ehl_pse_io_dev_release;
> +
> + ret = auxiliary_device_init(aux_dev);
> + if (ret)
> + goto free_io_dev;
> +
> + ret = __auxiliary_device_add(aux_dev, dev->driver->name);

Hmm... Is it okay to use double underscored variant? Only a single driver uses
this so far... Care to elaborate?

> + if (ret)
> + goto uninit_aux_dev;
> +
> + return 0;
> +
> +uninit_aux_dev:
> + /* io_dev will be freed with the put_device() and .release sequence */

Right...

> + auxiliary_device_uninit(aux_dev);
> +free_io_dev:
> + kfree(io_dev);

...and this is a double free, correct?

> + return ret;
> +}

--
With Best Regards,
Andy Shevchenko