Re: [RFC PATCH 02/06] input/rmi4: Core files

From: Christopher Heiny
Date: Tue Oct 23 2012 - 20:32:49 EST

On 10/23/2012 05:11 PM, Dmitry Torokhov wrote:
On Tuesday, October 23, 2012 04:46:28 PM Christopher Heiny wrote:
On 10/11/2012 01:13 AM, Dmitry Torokhov wrote:
On Thu, Oct 11, 2012 at 04:15:56AM +0000, Christopher Heiny wrote:
On Thursday, October 11, 2012 02:21:53 AM you wrote:
On Sat, Oct 6, 2012 at 6:09 AM, Christopher Heiny <cheiny@xxxxxxxxxxxxx>


+static int process_interrupt_requests(struct rmi_device *rmi_dev)
+ struct rmi_driver_data *data = dev_get_drvdata(&rmi_dev->dev);
+ struct device *dev = &rmi_dev->dev;
+ struct rmi_function_container *entry;
+ u8 irq_status[data->num_of_irq_regs];

Looking at this...

What does the data->num_of_irq_regs actually contain?

I just fear that it is something constant like always 2 or always 4,
so there is actually, in reality, a 16 or 32 bit register hiding in

In that case what you should do is to represent it as a u16 or u32 here,
just or the bits into a status word, and then walk over that status
word with something like ffs(bitword); ...

Nope, it's not constant. In theory, and RMI4 based sensor can have up
to 128 functions (in practice, it's far fewer), and each function can
have as many as 7 interrupts. So the number of IRQ registers can vary
from RMI4 sensor to RMI4 sensor, and needs to be computed during the
scan of the product descriptor table.

Is it a good idea to have it on stack then? Should it be part of
rmi_device instead?

It's not coming off the stack. We're allocating it via devm_kzalloc()
in rmi_driver_probe().

No, look at the part of the code that was quoted. "u8 irq_status[data-
num_of_irq_regs];" is on stack.

Sorry - I thought you were referring to data->num_of_irq_regs rather than irq_status. We'll move that.
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