linux-kernel - Re: [RFC PATCH 2/2] hwmon: (f71805f): Use request_region() in f71805f

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Date:   Thu, 14 Mar 2019 10:44:08 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     John Garry <john.garry@...wei.com>
Cc:     jdelvare@...e.com, bhelgaas@...gle.com, rafael@...nel.org,
        arnd@...db.de, lorenzo.pieralisi@....com, bp@...e.de,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, wangkefeng.wang@...wei.com,
        linuxarm@...wei.com
Subject: Re: [RFC PATCH 2/2] hwmon: (f71805f): Use request_region() in
 f71805f_init()

On Thu, Mar 14, 2019 at 05:21:32PM +0000, John Garry wrote:
> On 14/03/2019 17:05, Guenter Roeck wrote:
> >On Fri, Mar 15, 2019 at 12:55:16AM +0800, John Garry wrote:
> >>Currently the driver does not call request_region() prior to
> >>accessing IO port regions in f71805f_init(), so add it.
> >>
> >>Signed-off-by: John Garry <john.garry@...wei.com>
> >>---
> >> drivers/hwmon/f71805f.c | 13 ++++++++++++-
> >> 1 file changed, 12 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/drivers/hwmon/f71805f.c b/drivers/hwmon/f71805f.c
> >>index 73c681162653..910082c7f184 100644
> >>--- a/drivers/hwmon/f71805f.c
> >>+++ b/drivers/hwmon/f71805f.c
> >>@@ -1617,10 +1617,21 @@ static int __init f71805f_init(void)
> >> 	int err;
> >> 	unsigned short address;
> >> 	struct f71805f_sio_data sio_data;
> >>+	struct resource *res;
> >>+	size_t size = 0x4e - 0x2e + SIO_REG_ADDR + 4;
> >>+
> >>+	/* Request the whole 0x2e - 0x4e region */
> >>+	res = request_region(0x2e, size, "f71805f");
> >
> 
> Hi Guenter,
> 
> >request_muxed_region() would be a better choice here since it doesn't
> >bail out immediately if the region is temporarily busy.
> 
> Are you saying that this region could be busy due to another driver
> accessing this same region (probably for the same purpose)?
> 
Depends on the definition of "same reason". To access the chip's
Super-IO configuration registers, yes, that can happen. I don't
see it used in the kernel today, but examples would be someone
adding support for the chips supported by this driver to gpio-f7188x,
or adding support for the F71872 watchdog to the f71808e_wdt driver.

Guenter