Re: [PATCH net-next v17 01/13] rtase: Add pci table supported in this module

From: Simon Horman
Date: Fri May 03 2024 - 05:33:45 EST


On Thu, May 02, 2024 at 05:18:35PM +0800, Justin Lai wrote:
> Add pci table supported in this module, and implement pci_driver function
> to initialize this driver, remove this driver, or shutdown this driver.
>
> Signed-off-by: Justin Lai <justinlai0215@xxxxxxxxxxx>

..

> diff --git a/drivers/net/ethernet/realtek/rtase/rtase_main.c b/drivers/net/ethernet/realtek/rtase/rtase_main.c
> new file mode 100644
> index 000000000000..5ddb5f7abfe9
> --- /dev/null
> +++ b/drivers/net/ethernet/realtek/rtase/rtase_main.c
> @@ -0,0 +1,618 @@
> +// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
> +/*
> + * rtase is the Linux device driver released for Realtek Automotive Switch
> + * controllers with PCI-Express interface.
> + *
> + * Copyright(c) 2023 Realtek Semiconductor Corp.
> + *
> + * Below is a simplified block diagram of the chip and its relevant interfaces.
> + *
> + * *************************
> + * * *
> + * * CPU network device *
> + * * *
> + * * +-------------+ *
> + * * | PCIE Host | *
> + * ***********++************
> + * ||
> + * PCIE
> + * ||
> + * ********************++**********************
> + * * | PCIE Endpoint | *
> + * * +---------------+ *
> + * * | GMAC | *
> + * * +--++--+ Realtek *
> + * * || RTL90xx Series *
> + * * || *
> + * * +-------------++----------------+ *
> + * * | | MAC | | *
> + * * | +-----+ | *
> + * * | | *
> + * * | Ethernet Switch Core | *
> + * * | | *
> + * * | +-----+ +-----+ | *
> + * * | | MAC |...........| MAC | | *
> + * * +---+-----+-----------+-----+---+ *
> + * * | PHY |...........| PHY | *
> + * * +--++-+ +--++-+ *
> + * *************||****************||***********

Thanks for the diagram, I like it a lot :)

> + *
> + * The block of the Realtek RTL90xx series is our entire chip architecture,
> + * the GMAC is connected to the switch core, and there is no PHY in between.
> + * In addition, this driver is mainly used to control GMAC, but does not
> + * control the switch core, so it is not the same as DSA.
> + */

..

> +static int rtase_alloc_msix(struct pci_dev *pdev, struct rtase_private *tp)
> +{
> + int ret;
> + u16 i;
> +
> + memset(tp->msix_entry, 0x0, RTASE_NUM_MSIX * sizeof(struct msix_entry));
> +
> + for (i = 0; i < RTASE_NUM_MSIX; i++)
> + tp->msix_entry[i].entry = i;
> +
> + ret = pci_enable_msix_exact(pdev, tp->msix_entry, tp->int_nums);
> + if (!ret) {

In Linux Networking code it is an idiomatic practice to keep
handle errors in branches and use the main path of execution
for the non error path.

In this case I think that would look a bit like this:

ret = pci_enable_msix_exact(pdev, tp->msix_entry, tp->int_nums);
if (ret)
return ret;

...

return 0;

> +
> + for (i = 0; i < tp->int_nums; i++)
> + tp->int_vector[i].irq = pci_irq_vector(pdev, i);

pci_irq_vector() can fail, should that be handled here?

> + }
> +
> + return ret;
> +}
> +
> +static int rtase_alloc_interrupt(struct pci_dev *pdev,
> + struct rtase_private *tp)
> +{
> + int ret;
> +
> + ret = rtase_alloc_msix(pdev, tp);
> + if (ret) {
> + ret = pci_enable_msi(pdev);
> + if (ret)
> + dev_err(&pdev->dev,
> + "unable to alloc interrupt.(MSI)\n");

If an error occurs then it is a good practice to unwind resource
allocations made within the context of this function call, as this
leads to more symmetric unwind paths in callers.

In this case I think any resources consumed by rtase_alloc_msix()
should be released if pci_enable_msi fails. Probably using
a goto label is appropriate here.

Likewise, I suggest that similar logic applies to errors within
rtase_alloc_msix().

> + else
> + tp->sw_flag |= RTASE_SWF_MSI_ENABLED;
> + } else {
> + tp->sw_flag |= RTASE_SWF_MSIX_ENABLED;
> + }
> +
> + return ret;
> +}

..