linux-kernel - Re: [PATCH v9 tty-next 2/4] serial: 8250_pci1xxxx: Add driver for quad-uart support

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Date:   Thu, 15 Dec 2022 19:42:32 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Kumaravel Thiagarajan <kumaravel.thiagarajan@...rochip.com>
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        gregkh@...uxfoundation.org, jirislaby@...nel.org,
        ilpo.jarvinen@...ux.intel.com, macro@...am.me.uk, cang1@...e.co.uk,
        colin.i.king@...il.com, phil.edworthy@...esas.com,
        biju.das.jz@...renesas.com, geert+renesas@...der.be,
        lukas@...ner.de, u.kleine-koenig@...gutronix.de, wander@...hat.com,
        etremblay@...tech-controls.com, jk@...abs.org,
        UNGLinuxDriver@...rochip.com,
        Tharun Kumar P <tharunkumar.pasumarthi@...rochip.com>
Subject: Re: [PATCH v9 tty-next 2/4] serial: 8250_pci1xxxx: Add driver for
 quad-uart support

On Fri, Dec 16, 2022 at 10:56:54AM +0530, Kumaravel Thiagarajan wrote:
> pci1xxxx is a PCIe switch with a multi-function endpoint on one of
> its downstream ports. Quad-uart is one of the functions in the
> multi-function endpoint. This driver loads for the quad-uart and
> enumerates single or multiple instances of uart based on the PCIe
> subsystem device ID.

...

> +static const int logical_to_physical_port_idx[][MAX_PORTS] = {
> +	{0,  1,  2,  3},/* PCI12000, PCI11010, PCI11101, PCI11400, PCI11414 */
> +	{0,  1,  2,  3},/* PCI4p */
> +	{0,  1,  2, -1},/* PCI3p012 */
> +	{0,  1,  3, -1},/* PCI3p013 */
> +	{0,  2,  3, -1},/* PCI3p023 */
> +	{1,  2,  3, -1},/* PCI3p123 */
> +	{0,  1, -1, -1},/* PCI2p01 */
> +	{0,  2, -1, -1},/* PCI2p02 */
> +	{0,  3, -1, -1},/* PCI2p03 */
> +	{1,  2, -1, -1},/* PCI2p12 */
> +	{1,  3, -1, -1},/* PCI2p13 */
> +	{2,  3, -1, -1},/* PCI2p23 */
> +	{0, -1, -1, -1},/* PCI1p0 */
> +	{1, -1, -1, -1},/* PCI1p1 */
> +	{2, -1, -1, -1},/* PCI1p2 */
> +	{3, -1, -1, -1},/* PCI1p3 */

One space or TAB before /* will increase readability.

> +};

...

> +	ret = serial8250_pci_setup_port(pdev, port, 0, port_idx * 256, 0);

Actually isn't 0x100 better (show that there is an offset rather than
a value of an register)?

> +	if (ret < 0)
> +		return ret;

...

> +static unsigned int pci1xxxx_get_max_port(int subsys_dev)
> +{
> +	int i = 0;

What the point to assign this one?

Actually, better is

	unsigned int = MAX_PORTS;

> +	if (subsys_dev < ARRAY_SIZE(logical_to_physical_port_idx))

> +		for (i = MAX_PORTS - 1; i >= 0; i--)

while (i--) {

> +			if (logical_to_physical_port_idx[subsys_dev][i] != -1)
> +				return logical_to_physical_port_idx[subsys_dev][i] + 1;

}

(Note missinng {} in the above code. Does checkpatch complain on this?)

> +
> +	if (subsys_dev != PCI_SUBDEVICE_ID_EFAR_PCI11414)
> +		return 1;
> +
> +	return 4;
> +}

...

> +	num_vectors = pci_alloc_irq_vectors(pdev, 1, max_vec_reqd, PCI_IRQ_ALL_TYPES);
> +	if (num_vectors < 0) {

> +		pci_iounmap(pdev, priv->membase);

Here is inconsistency on how you interpret pci_*() calls when
pcim_enable_device() has been used. I.e. for IRQ you don't
deallocate resources explicitly (yes, it's done automatically
anyway), but you explicitly call pci_iounmap(). Choose a single
approach for all of them.

> +		return num_vectors;
> +	}

...

> +static_assert((ARRAY_SIZE(logical_to_physical_port_idx) ==
> +	       PCI_SUBDEVICE_ID_EFAR_PCI1XXXX_1p3 + 1));

Can be still one line.

-- 
With Best Regards,
Andy Shevchenko