Hello.
And thanks to Andrew for the comments.
>> include/linux/pn544.h | 99 ++++++
>
> Is drivers/misc/ the best place for this?
>
> Don't be afraid to create a new drivers/nfc/ even if it has only one
> driver in it. If someone later comes in and adds a new NFC driver then
> things will all fall into place.
OK. Now I've created directories drivers/nfc, include/linux/nfc and
Documentation/nfc.
>> + Say yes if you want PN544 Near Field Communication driver.
>
> OK, I did google it ;) Interesting.
I agree... ;-)
>> + pr_info("\n");
>
> You might be able to use print_hex_dump() here, but I wouldn't blame
> you if you didn't ;)
I replaced the debug function with calls to print_hex_dump.
>> +/* sysfs interface */
>
> OK, this is more serious.
>
> You're proposing a permanent addition to the kernel ABI. This is the
> most important part of the driver because it is something we can never
> change. This interface is the very first thing we'll want to
> understand and review, before we even look at the implementation.
>
> And it isn't even described! Not in the changelog, not in a
> documentation file, not even in code comments.
>
> Please, provide a description of this proposed interface. Sufficient
> for reviewers to understand it and for users to use it. Pobably this
> will require some description of the hardware functions as well.
>
> Please also consider updating Documentation/ABI/
I've added a documentation file. But I didn't make changes to the interface
yet.
>> + GFP_KERNEL);
>
> From my reading, later code will crash the kernel if this allocation failed.
>
> Also, is there a race here between reading info->fw_buf and setting it?
> Can two CPUs get into thei function at the same time? If so, there
> should be locking. Say, a mutex local to this function.
I moved the data buffer allocation to probe and also changed the locking.
>> + return -EBADMSG;
>
> EBADMSG is a unix streams errno. It's quite inappropriate that a
> device driver be using it. Imagine the poor user's confution if he
> sees this message pop up on his screen.
Changed to EINVAL.
>> + if (r == -EREMOTEIO) { /* Retry, chip was in standby */
>
> And what on earth is EREMOTEIO? Is it appropriate for use in a driver?
I think it is, because it comes from i2c_master_send and it's kind of
just forwarded here.
>> + return -EOVERFLOW;
>
> EOVERFLOW refers to a floating point overflow!
It's used for buffer overflow in many places in the kernel, but that's
not an excuse so I removed it.
>> + return -ENOSPC;
>
> Disk full!
Also removed...
>> + mutex_unlock(&info->read_mutex);
>
> It usually doesn't make much sense to add locking around a single
> atomic read instruction.
Yes, but if there's a sequence of instructions somewhere else in the
code that the single instruction is not allowd to intersect then it
can be valid.
>> + size_t count, loff_t *offset)
>
> Again, I really cannot review this code when I haven't been told what
> it's reading from, what's in the payload, what it is all to be used
> for, etc. It's just C code to me.
>
I've added a documentation file to explain things but basically the
driver doesn't much care about the data it passes through, apart from
message lengths and check sums.
>> + len = min(count, (size_t) PN544_MAX_I2C_TRANSFER);
>
> min_t() is the preferred way of solving this.
Good to know, but because of a code change it wasn't necessary.
> +}
>
> So it can poll() somethnig as well! This driver *really* needs
> documentation!
>
Yes, you can wait for something to read.
>> + if (info->state == PN544_ST_FW_READY) {
>
> Is some locking needed here? What prevents info->state from
> transitioning while this code is executing?
Locking added.
>> +static long pn544_ioctl(struct file *file, unsigned int cmd, unsigned long
>> arg)
>
> And an ioctl interface as well! An undocmented one.
>
> ioctls are pretty unpopular for various reasons. To a large extent,
> people have been using sysfs interfaces as a repalcement for ioctl()s.
> But this driver has both!
Some explanatory text written into the documentation file.
> Does this code need compat handling, or it is 32/64-bit clean?
I think it is...
>> + pn544_disable(info);
>
> bug. pn544_disable() calls msleep(), but msleep() is very illegal
> under spin_lock_irqsave(). This tells me that this code hasn't been
> tested with even rudimentary kernel rimtime debugging options enabled.
> Documentation/SubmitChecklist section 12 is fairly up-to-date here.
Removed spinlocks and in general revised the locking...
>> + pn544_disable(info);
>
> Many more such bugs there.
Well, yes...
>> +#ifdef DO_RSET_TEST
>
> I'd suggest enabling this via a module parameter if it's at all useful.
> Otherwise it should be enabled with a Kconfig variable, not via a code
> edit.
Removed the test...
>> + flush_scheduled_work();
>
> This seems unneeded? We're trying to get rid of flush_scheduled_work(), btw.
Removed flush_scheduled_work...
Cheers,
Matti
Matti J. Aaltonen (1):
NFC: Driver for NXP Semiconductors PN544 NFC chip.
Documentation/nfc/nfc-pn544.txt | 105 +++++
drivers/Kconfig | 2 +
drivers/Makefile | 2 +-
drivers/nfc/Kconfig | 30 ++
drivers/nfc/Makefile | 5 +
drivers/nfc/pn544.c | 893 +++++++++++++++++++++++++++++++++++++++
include/linux/nfc/pn544.h | 99 +++++
7 files changed, 1135 insertions(+), 1 deletions(-)
create mode 100644 Documentation/nfc/nfc-pn544.txt
create mode 100644 drivers/nfc/Kconfig
create mode 100644 drivers/nfc/Makefile
create mode 100644 drivers/nfc/pn544.c
create mode 100644 include/linux/nfc/pn544.h
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