Re: [PATCH V1 3/4] usb: serial: f81534: add output pin control

[Ji-Ze Hong (Peter Hong)]

Hi Johan,

Johan Hovold æ 2017/12/19 äå 12:06 åé:
> On Thu, Nov 16, 2017 at 03:46:08PM +0800, Ji-Ze Hong (Peter Hong) wrote:
> > +static int f81534_set_port_output_pin(struct usb_serial_port *port)
> > +{
> > +	struct f81534_serial_private *serial_priv;
> > +	struct f81534_port_private *port_priv;
> > +	struct usb_serial *serial;
> > +	const struct f81534_port_out_pin *pins;
> > +	int status;
> > +	int i;
> > +	u8 value;
> > +	u8 idx;
> > +
> > +	serial = port->serial;
> > +	serial_priv = usb_get_serial_data(serial);
> > +	port_priv = usb_get_serial_port_data(port);
> > +
> > +	idx = F81534_CONF_GPIO_OFFSET + port_priv->phy_num;
> > +	value = serial_priv->conf_data[idx];
> > +	pins = &f81534_port_out_pins[port_priv->phy_num];
> > +
> > +	for (i = 0; i < ARRAY_SIZE(pins->pin); ++i) {
> > +		status = f81534_set_mask_register(serial,
> > +				pins->pin[i].reg_addr, pins->pin[i].reg_mask,
> > +				value & BIT(i) ? pins->pin[i].reg_mask : 0);
> > +		if (status)
> > +			return status;
> > +	}
>
> You're using 24 (get or set) accesses to update these three registers
> here. Why not read them out (if necessary), determine their new values
> and then write them back when done instead?

In this code, I'm only read/write 3 registers of 0x2ae8, 0x2a90, 0x2a80,
but some register will read/write more than once. Should I change the
code from port_probe() to attach() and re-write it as:
	1: read the 3 register
	2: change them will 12 pin desire value
	3: write it back
Is it ok?

Thanks
--
With Best Regards,
Peter Hong