linux-kernel - Re: [PATCH 1/3 v2] mfd: Add LPC driver for Intel ICH chipsets

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Date:	Tue, 07 Feb 2012 15:00:55 -0600 (CST)
From:	Aaron Sierra <asierra@...-inc.com>
To:	guenter roeck <guenter.roeck@...csson.com>
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Tyser <ptyser@...-inc.com>
Subject: Re: [PATCH 1/3 v2] mfd: Add LPC driver for Intel ICH chipsets

> > +static int __devinit lpc_ich_probe(struct pci_dev *dev,
> > +                               const struct pci_device_id *id)
> > +{
> > +       u32 base_addr_cfg;
> > +       u32 base_addr;
> > +       u8 reg_save;
> > +       int ret;
> > +       int cells = 0;
> > +       int acpi_conflict = 0;
> > +
> You can use bool for acpi_conflict (and cells, but I don't think that
> is needed anyway).

I agree that bool is a better type choice. See my comment at the end
regarding my reason for using cells.


> > +pm_done:
> > +       /* Setup GPIO base register */
> > +       pci_read_config_dword(dev, GPIOBASE, &base_addr_cfg);
> > +       base_addr = base_addr_cfg & 0x0000ff80;
> > +       if (!base_addr) {
> > +               dev_err(&dev->dev, "I/O space for GPIO
> > uninitialized\n");
> > +               /* GPIO in power-management space may still be
> > available */
> > +               goto gpio_reg;
> > +       }
> > +
> > +       gpio_ich_res[ICH_RES_GPIO].start = base_addr;
> > +       gpio_ich_res[ICH_RES_GPIO].end = base_addr +
> > GPIOBASE_IO_SIZE - 1;
> > +       ret =
> > acpi_check_resource_conflict(&gpio_ich_res[ICH_RES_GPIO]);
> > +       if (ret) {
> > +               /* this isn't necessarily fatal for the GPIO */
> > +               gpio_ich_res[ICH_RES_GPIO].start = 0;
> > +               gpio_ich_res[ICH_RES_GPIO].end = 0;
> > +               acpi_conflict++;
> 
> 	acpi_conflict = true;
> 
> After all, it does not really matter how many conflicts were
> detected.

I agree.

> > +gpio_reg:
> > +       lpc_ich_finalize_cell(&lpc_ich_cells[LPC_GPIO], id);
> > +       ret = mfd_add_devices(&dev->dev, 0,
> > &lpc_ich_cells[LPC_GPIO],
> > +                               1, NULL, 0);
> > +       if (!ret)
> > +               cells++;
> > +
> So if there is an error, ret < 0, correct ?
> 
> > +       if (acpi_conflict)
> > +               dev_info(&dev->dev, "ACPI resource conflicts found;
> > "
> > +                               "consider using
> > acpi_enforce_resources=lax?\n");
> > +
> > +       if (cells)
> > +               return 0;
> > +       else
> > +               return -ENODEV;
> 
> If the above is true, you can just return ret, and you don't need the
> cells variable. Or, even better, move the acpi warning above the call
> to mfd_add_devices().

The cells variable isn't strictly necessary when we're only dealing
with one cell registration, as we have if only looking at the lpc_ich
and gpio-ich patches. The iTCO_wdt patch adds a second call to
mfd_add_devices, so when we return we're interested if either of the
calls succeeded. This was intended to be a forward thinking
implementation, but I have no qualms about simplifying it in the
initial lpc_ich patch.
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