linux-kernel - Re: [PATCH v3 5/7] mfd: ioc3: Add driver for SGI IOC3 chip

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Date:   Mon, 29 Jul 2019 20:45:57 +0200
From:   Thomas Bogendoerfer <tbogendoerfer@...e.de>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        netdev@...r.kernel.org, linux-rtc@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH v3 5/7] mfd: ioc3: Add driver for SGI IOC3 chip

On Thu, 25 Jul 2019 12:47:16 +0100
Lee Jones <lee.jones@...aro.org> wrote:

> On Thu, 13 Jun 2019, Thomas Bogendoerfer wrote:
> > +/*
> > + * On IP30 the RTC (a DS1687) is behind the IOC3 on the generic
> > + * ByteBus regions. We have to write the RTC address of interest to
> > + * IOC3_BYTEBUS_DEV1, then read the data from IOC3_BYTEBUS_DEV2.
> > + * rtc->regs already points to IOC3_BYTEBUS_DEV1.
> > + */
> > +#define IP30_RTC_ADDR(rtc) (rtc->regs)
> > +#define IP30_RTC_DATA(rtc) ((rtc->regs) + IOC3_BYTEBUS_DEV2 - IOC3_BYTEBUS_DEV1)
> > +
> > +static u8 ip30_rtc_read(struct ds1685_priv *rtc, int reg)
> > +{
> > +	writeb((reg & 0x7f), IP30_RTC_ADDR(rtc));
> > +	return readb(IP30_RTC_DATA(rtc));
> > +}
> > +
> > +static void ip30_rtc_write(struct ds1685_priv *rtc, int reg, u8 value)
> > +{
> > +	writeb((reg & 0x7f), IP30_RTC_ADDR(rtc));
> > +	writeb(value, IP30_RTC_DATA(rtc));
> > +}
> 
> Why is this not in the RTC driver?

because rtc1685 is used in different systems and accessing the chip
differs between those systems. 

> > +static struct ds1685_rtc_platform_data ip30_rtc_platform_data = {
> > +	.bcd_mode = false,
> > +	.no_irq = false,
> > +	.uie_unsupported = true,
> > +	.alloc_io_resources = true,
> 
> > +	.plat_read = ip30_rtc_read,
> > +	.plat_write = ip30_rtc_write,
> 
> Call-backs in a non-subsystem API is pretty ugly IMHO.

I agree

> Where are these called from?

drivers/rtc/rtc-ds1685.c

I could do the same as done for serial8250 and add an additional .c file
in  drivers/rtc which handles this for SGI-IP30. Alexandre would this work
for you as well ?

> > +#define IOC3_SID(_name, _sid, _setup) \
> > +	{								   \
> > +		.name = _name,						   \
> > +		.sid = (PCI_VENDOR_ID_SGI << 16) | IOC3_SUBSYS_ ## _sid,   \
> > +		.setup = _setup,					   \
> > +	}
> > +
> > +static struct {
> > +	const char *name;
> > +	u32 sid;
> > +	int (*setup)(struct ioc3_priv_data *ipd);
> > +} ioc3_infos[] = {
> 
> IMHO it's neater if you separate the definition and static data part.

I don't quite understand what you mean here. Should I move the #define at
the beginning of the file ? Why is it neater ?

Thomas.

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