Hi Linus,
On 04/01/2016 07:17 AM, Linus Walleij wrote:
On Tue, Mar 29, 2016 at 9:13 PM, <tthayer@xxxxxxxxxxxxxxxxxxxxx> wrote:
From: Thor Thayer <tthayer@xxxxxxxxxxxxxxxxxxxxx>
Add the GPIO functionality for the Altera Arria10 MAX5 System Resource
Chip. The A10 MAX5 has 12 bits of GPIO assigned to switches, buttons,
and LEDs as a GPIO extender on the SPI bus.
Signed-off-by: Thor Thayer <tthayer@xxxxxxxxxxxxxxxxxxxxx>
OK...
As Lee says: split off the MFD patch so it is a pure GPIO driver
patch.
ACK
+#include <linux/gpio.h>
You should instead #include <linux/gpio/driver.h>
+#include <linux/mfd/altera-a10sr.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/seq_file.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
Syscalls and uaccess??? I don't think so.
OK.
+struct altr_a10sr_gpio {
+ struct altr_a10sr *a10sc;
+ struct gpio_chip gp;
+};
Add some kerneldoc.
OK. To clarify, is this comment referring to the bindings document or
something different?
+static inline struct altr_a10sr_gpio *to_altr_a10sr_gpio(struct gpio_chip *chip)
+{
+ return container_of(chip, struct altr_a10sr_gpio, gp);
+}
Don't use this old design pattern.
Use [devm_]gpiochip_add_data() and use gpiochip_get_data(gc) to get
a data pointer from the gpiochip.
+static int altr_a10sr_gpio_get(struct gpio_chip *gc, unsigned int nr)
+{
+ struct altr_a10sr_gpio *gpio = to_altr_a10sr_gpio(gc);
So this becomes
struct altr_a10sr_gpio *gpio = gpiochip_get_data(gc);
Got it. Thanks!
+ int ret;
+ unsigned char reg = ALTR_A10SR_LED_RD_REG + ALTR_A10SR_REG_OFFSET(nr);
+
+ ret = altr_a10sr_reg_read(gpio->a10sc, reg);
+
+ if (ret < 0)
+ return ret;
+
+ if (ret & (1 << ALTR_A10SR_REG_BIT(nr)))
+ return 1;
Do this instead:
return !!(ret & (1 << ALTR_A10SR_REG_BIT(nr)))
It raises the question whether ALTR_A10SR_REG_BIT
is just a reimplementation of the BIT() macro from
<linux/bitops.h>, please check this.
Got it. Yes, I will check that. Thanks.
+static int altr_a10sr_gpio_direction_input(struct gpio_chip *gc,
+ unsigned int nr)
+{
+ if ((nr >= ALTR_A10SR_IN_VALID_RANGE_LO) &&
+ (nr <= ALTR_A10SR_IN_VALID_RANGE_HI))
+ return 0;
+ return -EINVAL;
+}
+
+static int altr_a10sr_gpio_direction_output(struct gpio_chip *gc,
+ unsigned int nr, int value)
+{
+ if ((nr >= ALTR_A10SR_OUT_VALID_RANGE_LO) &&
+ (nr <= ALTR_A10SR_OUT_VALID_RANGE_HI))
+ return 0;
+ return -EINVAL;
+}
Does this mean that all lines are *always* input and output
at the same time?
If there is no .set_direction() callback and all lines are both
input and output it kind of implies that all lines are also
implicitly open drain do you agree?
Please check:
- If there is really no direction setting anywhere
- For example if some lines are hardwired as input and
some lines are hardwired as output
- If that is not the case, verify that all lines are really
open drain, they should be if all are both input and
output at the same time.
I see your point. I'll investigate how to do this properly for your 2nd
check above. Registers are hard-wired as input or output so I'll need to
handle this properly and is why I didn't implement the .set_direction
callback. Thanks for the explanation.
In my case, there are 12 valid GPIOs out of the 16 bits (the first 4
bits are unused). Bits 4-7 are output and bits 8-15 are inputs. I was
using the IN_VALID range for the inputs and the OUT_VALID range for the
outputs.
+ ret = gpiochip_add(&gpio->gp);
+ if (ret < 0) {
+ dev_err(&pdev->dev, "Could not register gpiochip, %d\n", ret);
+ return ret;
+ }
Use devm_gpiochip_add_data() instead.
OK. Thanks for reviewing!
Yours,
Linus Walleij
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