Re: Extend device driver?

2016-09-10 Thread Greg KH 
On Sat, Sep 10, 2016 at 04:41:34PM +0200, Pol Eyschen wrote:
> Hi everyone,
> 
> I want to implement some custom functions of my mouse (Madcatz RAT5) in 
> Linux, e.g custom DPI-values. As this requires writing over USB to the 
> firmware of the mouse I was thinking of writing a module to accomplish 
> this. However I don't want to reimplement a whole mouse-driver,so I 
> wanted to ask if there is a possibility of binding the device to 2 
> modules or having my module extend usbhid, so that my module would only 
> be used to perform these custom operations while usbhid stays in charge 
> of the whole "mouse business".

Please just use the hidraw userspace driver/library instead, that way
you don't have to unbind the kernel driver and everything should work
just fine without having to touch the kernel at all.

Hope this helps,

greg k-h

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Extend device driver?

2016-09-10 Thread Pol Eyschen 
Hi everyone,

I want to implement some custom functions of my mouse (Madcatz RAT5) in 
Linux, e.g custom DPI-values. As this requires writing over USB to the 
firmware of the mouse I was thinking of writing a module to accomplish 
this. However I don't want to reimplement a whole mouse-driver,so I 
wanted to ask if there is a possibility of binding the device to 2 
modules or having my module extend usbhid, so that my module would only 
be used to perform these custom operations while usbhid stays in charge 
of the whole "mouse business".


Thanks

Pol


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Re: Extend device driver?

2016-09-10 Thread Daniel. 
You may want to look at http://www.signal11.us/oss/hidapi/ too, it has
nice interface to HID device and supports libusb and hidraw backends
(y)

Regards,

2016-09-10 12:14 GMT-03:00 Greg KH :
> On Sat, Sep 10, 2016 at 04:41:34PM +0200, Pol Eyschen wrote:
>> Hi everyone,
>>
>> I want to implement some custom functions of my mouse (Madcatz RAT5) in
>> Linux, e.g custom DPI-values. As this requires writing over USB to the
>> firmware of the mouse I was thinking of writing a module to accomplish
>> this. However I don't want to reimplement a whole mouse-driver,so I
>> wanted to ask if there is a possibility of binding the device to 2
>> modules or having my module extend usbhid, so that my module would only
>> be used to perform these custom operations while usbhid stays in charge
>> of the whole "mouse business".
>
> Please just use the hidraw userspace driver/library instead, that way
> you don't have to unbind the kernel driver and everything should work
> just fine without having to touch the kernel at all.
>
> Hope this helps,
>
> greg k-h
>
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-- 
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Status/Progress of CherryTrail / BayTrail support in mainline Linux kernel

2016-09-10 Thread Hanno Zulla 
Hi,

sorry for asking a possibly obvious question, but:

Why is support for Cherry Trail / Bay Trail so bad in the mainline
kernel? Is this being worked on? And where can one help or track the
progress with improving this?

Recently, I bought a Win10 netbook to install Linux on. It's a
beautiful small device with a fanless Z3735F CPU. Just right for my
kids as their first own computer.

After using Intel hardware since several years without a hitch, it was
surprising to find this not being fully supported by current 2016 Linux
distributions.

The Wifi is not running at all, lost the network with a Wifi stick that
works fine on RPi and the system freezes every now and then for no
reproducible reasons. Googling around, all I found were similar
complaints by other Linux users and a confusing array of incomplete
third-party driver projects not ready for mainline, like this one:

https://github.com/hadess/rtl8723bs/issues/96

Also, there's a litany of "don't buy Cherry Trail or Bay Trail devices
for Linux" articles, which probably would have been helpful to read
before buying that fateful device.

This is sad to watch. I tried to find a different device for my kids,
but all of the netbook-like devices on the market now share this
problem. A whole generation of very interesting devices appears to be
lost for Linux users.

Is there hope for this device class or does one have to stick to Core i
CPUs for the time being?

Kind regards,

Hanno

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Linux Security Module listsecurity (and security xattr hooks) only one called?

2016-09-10 Thread Pasquier, Thomas 
In security/security.c (see here:
https://github.com/torvalds/linux/blob/835c92d43b29eb354abdbd5475308a474d7efdfa/security/security.c
)

Looking at this:

int security_inode_listsecurity(struct inode *inode, char *buffer, size_t
buffer_size)
{
if (unlikely(IS_PRIVATE(inode)))
return 0;
return call_int_hook(inode_listsecurity, 0, inode, buffer, buffer_size);
}
One would expect all stacked security module to be called. However, when
looking at this:

#define call_int_hook(FUNC, IRC, ...) ({\
int RC = IRC;   \
do {\
struct security_hook_list *P;   \
\
list_for_each_entry(P, _hook_heads.FUNC, list) { \
RC = P->hook.FUNC(__VA_ARGS__); \
if (RC != 0)\
break;  \
}   \
} while (0);\
RC; \
})
If one of the module return a non-zero value, the other are not called.
That means that the list of security of xattr is not built (or rather that
it only contains the first module being called), as the lenght of inserted
element is returned. Similarly for setsecurity and getsecurity, it seems
that only one module will be called as if the given module does not support
the security xattr, it returns -EOPNOTSUPP (instead I believe the next
module being called, until one supporting the attribute is met).

What is the rational here? I could change the code to support multiple
security xattr, but don't want to do so before I understand why it was done
like this. Any help is welcome.
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memblock_reserve or memblock_remove to reserve a page

2016-09-10 Thread Nikhil Utane 
I want to reserve a physical memory page with a fixed PFN. I do not want
this page to be used by anyone else. I am calling memblock_reserve() to
supposedly reserve the page. I am writing some content into this page. What
I see is that during some runs the content of this page is modified (either
fully or sometimes partially). In few runs, I see it as intact. Is it
expected that even after calling memblock_reserve() the kernel can allocate
this physical page for any other purpose? How is memblock_remove()
different from memblock_reserve? I tried reading up but didn't see any
useful information. What I understood is memblock_remove will completely
remove from kernel's allocation mechanism. Should I then be using remove
instead of reserve?

-Thanks
Nikhil
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Confused about rtnl routing mutex scalability

2016-09-10 Thread nick 
Greetings All,
I am curious as it after reading the network code for a while it seems that to 
me
at least the rtnl mutex lock is a bottleneck. Is there any reason that we are 
still
using a global mutex for all routing changes in the networking stack for the 
Linux
kernel or does it actually scale only, seems to me that it is causing nothing 
but
problems with deadlocks related to it or issues with locking timeouts on 
separate
netdev routing tables for two different networks. Is this just me or does this 
lock
actually cause serious issues or can do so.
Regards,
Nick

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Re: memblock_reserve or memblock_remove to reserve a page

2016-09-10 Thread Nikhil Utane 
Hi,

I want to reserve a physical memory page with a fixed PFN. I do not want
this page to be used by anyone else. I am calling memblock_reserve() to
supposedly reserve the page. I am writing some content into this page. What
I see is that during some runs the content of this page is modified (either
fully or sometimes partially). In few runs, I see it as intact. Is it
expected that even after calling memblock_reserve() the kernel can allocate
this physical page for any other purpose? How is memblock_remove()
different from memblock_reserve? I tried reading up but didn't see any
useful information. What I understood is memblock_remove will completely
remove from kernel's allocation mechanism. Should I then be using remove
instead of reserve?

-Thanks
Nikhil
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