Re: [RFC] Simple but effective way of changing HID device descriptors (resent)

[Marcin Tolysz <tolysz@gmail.com>]

Just to make sure the corrected patch is: [RFC v2] [HID] allow using
external Hid Descriptors.

2009/12/24 Antonio Ospite <ospite@studenti.unina.it>:
> On Thu, 24 Dec 2009 02:29:47 +0000
> Marcin Tolysz <tolysz@gmail.com> wrote:
>
>> Simple but effective way of changing HID device descriptors using
>> firmware loading mechanism.
>> Just place your new descriptor in a location specified by driver
>> i.e. somewhere in /lib/firmware/hid/
>> If it is there it will replace HID descriptor from the device.
>> I do not do any parsing or checking, as it is done by hid driver.
>>
>> Signed-off-by: Marcin Tolysz <tolysz@gmail.com>
>>
>
> Only some style comments below, I haven't tested the patch. Plus, try
> running the patch through scripts/checkpatch.pl to spot all the other
> style issues.

Corrected most of style errors but 3 too long lines.

>> ---
>>   drivers/hid/hid-core.c |   26 +++++++++++++++++++++++++-
>>   1 files changed, 25 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
>> index 80792d3..5d8d656 100644
>> --- a/drivers/hid/hid-core.c
>> +++ b/drivers/hid/hid-core.c
>> @@ -27,6 +27,7 @@
>>   #include <linux/wait.h>
>>   #include <linux/vmalloc.h>
>>   #include <linux/sched.h>
>> +#include <linux/firmware.h>
>>
>>   #include <linux/hid.h>
>>   #include <linux/hiddev.h>
>> @@ -640,6 +641,10 @@ int hid_parse_report(struct hid_device *device,
>> __u8 *start,
>>       struct hid_item item;
>>       __u8 *end;
>>       int ret;
>> +     const struct firmware *fw;
>> +     int succ;
>
> success? Can't you init fw to NULL and derive this info checking
> (fw != NULL) before releasing firmware?
every other driver checks this value, fw is a structure thus I would
need to check fw->data;

>> +     char *file;
>> +
>>       static int (*dispatch_type[])(struct hid_parser *parser,
>>                                     struct hid_item *item) = {
>>               hid_parser_main,
>> @@ -650,10 +655,27 @@ int hid_parse_report(struct hid_device *device,
>> __u8 *start,
>>
>>       if (device->driver->report_fixup)
>>               device->driver->report_fixup(device, start, size);
>> +     /* Now load a hid descriptor from a file firmware
>> +     ignoring this fixup thing */
>> +     file=kmalloc(29, GFP_KERNEL);
>> +
>> sprintf(file,"hid/%04X:%04X:%04X:%04X.bin",device->bus,device->vendor,device->product,device->version);
>> +
>
> What about removing this 29?
> #define NEW_HID_DESCRIPTOR_PATH_FMT "hid/%04X:%04X:%04X:%04X.bin"
> and use it in kmalloc with strlen and in sprintf.

replaced by:
       file = kasprintf(GFP_KERNEL, "hid/%04X:%04X:%04X:%04X.bin",
                      device->bus, device->vendor, device->product,
device->version);
I did not putted it into define as this heavily depends on parameters,
and I do not want to separate them yet.

>> +     succ = request_firmware(&fw, file, &device->dev);
>> +
>> +     if (succ)
>> +             printk(KERN_INFO "To relace HID descriptor place it in
>> /lib/firmaware/%s\n", file);
>
> pr_info() could be used or maybe even dev_info()

I went for pr_info.

>> +     else{
>> +             start = fw->data;
>> +             size = fw->size;
>> +             printk(KERN_INFO "HID descriptor relaced with /lib/firmaware/%s\n",
>> file);
>> +     }
>> +     kfree(file);
>>
>>       device->rdesc = kmalloc(size, GFP_KERNEL);
>> -     if (device->rdesc == NULL)
>> +     if (device->rdesc == NULL){
>> +             if(!succ)release_firmware(fw);
>>               return -ENOMEM;
>> +     }
>>       memcpy(device->rdesc, start, size);
>>       device->rsize = size;
>>
>> @@ -690,6 +712,7 @@ int hid_parse_report(struct hid_device *device, __u8
>> *start,
>>                               dbg_hid("unbalanced delimiter at end of report description\n");
>>                               goto err;
>>                       }
>> +                     if(!succ)release_firmware(fw);
>>                       vfree(parser);
>>                       return 0;
>>               }
>> @@ -697,6 +720,7 @@ int hid_parse_report(struct hid_device *device, __u8
>> *start,
>>
>>       dbg_hid("item fetching failed at offset %d\n", (int)(end - start));
>>   err:
>> +     if(!succ)release_firmware(fw);
>>       vfree(parser);
>>       return ret;
>>   }
>> -- 1.6.5.7
>
> Regards,
>   Antonio

Many thanks for your help.
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