On Fri, 10 Mar 2017, Li, Yi wrote:

> Hi Matthew
>
Hi Yi,


>
> On 3/10/2017 11:44 AM, matthew.gerlach@linux.intel.com wrote:
>> 
>> 
>> On Thu, 9 Mar 2017, yi1.li@linux.intel.com wrote:
>> 
>>> From: Yi Li <yi1.li@linux.intel.com>
>> 
>> 
>> Hi Yi,
>> 
>> Just one question below.
>> 
>> Matthew Gerlach
>> 
>> 
>>> Add function to load firmware in multiple chucks instead of
>>> 
>>> loading the whole big firmware file at once.
>>> 
>>> Signed-off-by: Yi Li <yi1.li@linux.intel.com>
>>> ---
>>> drivers/base/firmware_class.c | 128 
>>> ++++++++++++++++++++++++++++++++++++++++++
>>> include/linux/firmware.h      |   2 +
>>> 2 files changed, 130 insertions(+)
>>> 
>>> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
>>> index ac350c5..44fddff 100644
>>> --- a/drivers/base/firmware_class.c
>>> +++ b/drivers/base/firmware_class.c
>>> @@ -436,6 +436,62 @@ fw_get_filesystem_firmware(struct device *device, 
>>> struct firmware_buf *buf)
>>>     return rc;
>>> }
>>> 
>>> +static int
>>> +fw_stream_filesystem_firmware(struct device *device, struct firmware_buf 
>>> *buf,
>>> +            size_t offset, size_t length)
>>> +{
>>> +    int i, len;
>>> +    char *path;
>>> +    int rc = 0;
>>> +    struct file *file;
>>> +
>>> +    buf->size = 0;
>>> +
>>> +    path = __getname();
>>> +    if (!path)
>>> +        return -ENOMEM;
>>> +
>>> +    for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
>>> +        /* skip the unset customized path */
>>> +        if (!fw_path[i][0])
>>> +            continue;
>>> +
>>> +        len = snprintf(path, PATH_MAX, "%s/%s",
>>> +                   fw_path[i], buf->fw_id);
>> 
>> I'm probably being paranoid, but is it safe to assume the length of the 
>> buffer returned by __getname() is at least PATH_MAX?  It seems like
>> the length should be pagesize.
>
> The size should be the maximum number of char of the string be produced, not 
> the input size.
> According to 
> https://www.gnu.org/software/libc/manual/html_node/Formatted-Output-Functions.html
> Function:/int/*snprintf*/(char *s, size_tsize, const char *template, …)
> /The|snprintf|function is similar to|sprintf|, except that thesizeargument 
> specifies the maximum number of characters to produce. The trailing null 
> character is counted towards this limit, so you should allocate at 
> leastsizecharacters for the strings. Ifsizeis zero, nothing, not even the 
> null byte, shall be written andsmay be a null pointer.
> The return value is the number of characters which would be generated for the 
> given input, excluding the trailing null. If this value is greater than or 
> equal tosize, not all characters from the result have been stored ins
>

I am familiar with the functionality of snprintf versus sprintf.  In the
snprintf call above, you are saying that memory pointed to by the variable 
path, has at least PATH_MAX number of bytes.  My question is how can you 
know that the memory returned by __getname() has PATH_MAX number of bytes?


>> 
>>> +        if (len >= PATH_MAX) {
>>> +            rc = -ENAMETOOLONG;
>>> +            break;
>>> +        }
>>> +
>>> +        if (!path || !*path)
>>> +            continue;
>>> +
>>> +        if (!buf->data) {
>>> +            buf->data = vmalloc(length);
>>> +            if (!buf->data) {
>>> +                rc = -ENOMEM;
>>> +                break;
>>> +            }
>>> +        }
>>> +
>>> +        file = filp_open(path, O_RDONLY, 0);
>>> +        if (IS_ERR(file))
>>> +            continue;
>>> +
>>> +        buf->size = kernel_read(file, offset, (char *) buf->data,
>>> +                    length);
>>> +        fput(file);
>>> +        break;
>>> +    }
>>> +
>>> +    __putname(path);
>>> +
>>> +    if (rc)
>>> +        dev_err(device, "loading %s failed with error %d\n",
>>> +             path, rc);
>>> +    return rc;
>>> +}
>>> +
>>> /* firmware holds the ownership of pages */
>>> static void firmware_free_data(const struct firmware *fw)
>>> {
>>> @@ -1267,6 +1323,78 @@ request_firmware(const struct firmware 
>>> **firmware_p, const char *name,
>>> }
>>> EXPORT_SYMBOL(request_firmware);
>>> 
>>> +static int
>>> +_stream_firmware(const struct firmware **firmware_p, const char *name,
>>> +          struct device *device, void *buf, size_t size,
>>> +          unsigned int opt_flags, size_t offset, size_t length)
>>> +{
>>> +    int ret;
>>> +    struct firmware *fw = NULL;
>>> +    struct firmware_buf *fbuf;
>>> +
>>> +    if ((!firmware_p) || (!name || name[0] == '\0')) {
>>> +        dev_err(device, "invalid firmware pointer or file name\n");
>>> +        return -EINVAL;
>>> +    }
>>> +
>>> +    if (!*firmware_p) {
>>> +        ret = _request_firmware_prepare(&fw, name, device, buf, size);
>>> +        if (ret <= 0) {
>>> +            dev_err(device, "%s: _request_firmware_prepare failed %d\n",
>>> +                __func__, ret);
>>> +        }
>>> +    } else {
>>> +        fw = (struct firmware *) *firmware_p;
>>> +    }
>>> +
>>> +    fbuf = (struct firmware_buf *) fw->priv;
>>> +    ret = fw_stream_filesystem_firmware(device, fbuf, offset, length);
>>> +    fw->size = fbuf->size;
>>> +    fw->data = fbuf->data;
>>> +    *firmware_p = fw;
>>> +
>>> +    if (ret)
>>> +        dev_err(device, "streaming with error %d\n", ret);
>>> +    return ret;
>>> +}
>>> +
>>> +/**
>>> + * stream_firmware: - send firmware request and wait for it
>>> + * @firmware_p: pointer to firmware image
>>> + * @name: name of firmware file
>>> + * @device: device for which firmware is being loaded
>>> + * @offset: offset of the file to read from
>>> + * @length: length in bytes to read
>>> + *
>>> + *      @firmware_p will be used to return a firmware image by the name
>>> + *      of @name for device @device.
>>> + *
>>> + *      Should be called from user context where sleeping is allowed.
>>> + *
>>> + *      @name will be used as $FIRMWARE in the uevent environment and
>>> + *      should be distinctive enough not to be confused with any other
>>> + *      firmware image for this or any other device.
>>> + *
>>> + *    Caller must hold the reference count of @device.
>>> + *
>>> + *    The function can be called safely inside device's suspend and
>>> + *    resume callback.
>>> + **/
>>> +int
>>> +stream_firmware(const struct firmware **firmware_p, const char *name,
>>> +         struct device *device, size_t offset, size_t length)
>>> +{
>>> +    size_t ret;
>>> +
>>> +    /* Need to pin this module until return */
>>> +    __module_get(THIS_MODULE);
>>> +    ret = _stream_firmware(firmware_p, name, device, NULL, 0,
>>> +                FW_OPT_UEVENT | FW_OPT_NO_WARN, offset, length);
>>> +    module_put(THIS_MODULE);
>>> +    return ret;
>>> +}
>>> +EXPORT_SYMBOL(stream_firmware);
>>> +
>>> /**
>>>  * request_firmware_direct: - load firmware directly without usermode 
>>> helper
>>>  * @firmware_p: pointer to firmware image
>>> diff --git a/include/linux/firmware.h b/include/linux/firmware.h
>>> index b1f9f0c..accd7f6 100644
>>> --- a/include/linux/firmware.h
>>> +++ b/include/linux/firmware.h
>>> @@ -41,6 +41,8 @@ struct builtin_fw {
>>> #if defined(CONFIG_FW_LOADER) || (defined(CONFIG_FW_LOADER_MODULE) && 
>>> defined(MODULE))
>>> int request_firmware(const struct firmware **fw, const char *name,
>>>              struct device *device);
>>> +int stream_firmware(const struct firmware **fw, const char *name,
>>> +            struct device *device, size_t offset, size_t length);
>>> int request_firmware_nowait(
>>>     struct module *module, bool uevent,
>>>     const char *name, struct device *device, gfp_t gfp, void *context,
>>> -- 
>>> 2.7.4
>>> 
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