linux-kernel - Re: [PATCH] ata: add AMD Seattle platform driver

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Date:	Fri, 08 Jan 2016 11:59:53 -0800
From:	Joe Perches <joe@...ches.com>
To:	Brijesh Singh <brijesh.singh@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org, tj@...nel.org,
	devicetree@...r.kernel.org, linux-ide@...r.kernel.org
Subject: Re: [PATCH] ata: add AMD Seattle platform driver

On Thu, 2016-01-07 at 14:53 -0600, Brijesh Singh wrote:
> AMD Seattle SATA controller mostly conforms to AHCI interface with some
> special register to control SGPIO interface. In the case of an AHCI
> controller, the SGPIO feature is ideally implemented using the
> "Enclosure Management" register of the AHCI controller, but those
> registeres are not implemented in the Seattle SoC. Instead SoC
> (Rev B0 onwards) provides a 32-bit SGPIO control register which should
> be programmed to control the activity, locate and fault LEDs.

trivia:

> diff --git a/drivers/ata/ahci_seattle.c b/drivers/ata/ahci_seattle.c
[]
> +static ssize_t seattle_transmit_led_message(struct ata_port *ap, u32 state,
> +					    ssize_t size)
> +{
> +	struct ahci_host_priv *hpriv = ap->host->private_data;
> +	struct ahci_port_priv *pp = ap->private_data;
> +	struct seattle_plat_data *plat_data = hpriv->plat_data;
> +	unsigned long flags;
> +	int pmp;
> +	struct ahci_em_priv *emp;
> +	u32 val;
> +
> +	/* get the slot number from the message */
> +	pmp = (state & EM_MSG_LED_PMP_SLOT) >> 8;
> +	if (pmp < EM_MAX_SLOTS)
> +		emp = &pp->em_priv[pmp];
> +	else
> +		return -EINVAL;

This is generally done using a inverted test that
returns immediately

	if (pmp >= EMP_MAX_SLOTS)
		return -EINVAL;

	emp = &pp->em_priv[pmp];