linux-kernel - Re: [PATCH v3 1/3] lib/string: introduce ascii2utf16le() helper

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Date:   Wed, 8 Feb 2017 09:33:31 +0100
From:   Richard Leitner <richard.leitner@...data.com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        <linux-usb@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <gregkh@...uxfoundation.org>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <akpm@...ux-foundation.org>,
        <andriy.shevchenko@...ux.intel.com>, <keescook@...omium.org>,
        <dev@...l1n.net>
Subject: Re: [PATCH v3 1/3] lib/string: introduce ascii2utf16le() helper

On 02/06/2017 05:48 PM, Sergei Shtylyov wrote:
> Hello!
> 
> On 02/06/2017 05:03 PM, Richard Leitner wrote:
> 
>> For USB string descriptors we need to convert ASCII strings to UTF16-LE.
>> Therefore make a simple helper function (based on ascii2desc from
>> drivers/usb/core/hcd.c) for that purpose.
>>
>> Signed-off-by: Richard Leitner <richard.leitner@...data.com>
> [...]
>> diff --git a/lib/string.c b/lib/string.c
>> index ed83562..a113e3e 100644
>> --- a/lib/string.c
>> +++ b/lib/string.c
>> @@ -952,3 +952,29 @@ char *strreplace(char *s, char old, char new)
>>      return s;
>>  }
>>  EXPORT_SYMBOL(strreplace);
>> +
>> +/**
>> + * ascii2utf16le() - Helper routine for producing UTF-16LE string
>> descriptors
>> + * @s: Null-terminated ASCII (actually ISO-8859-1) string
>> + * @buf: Buffer for UTF-16LE string
>> + * @len: Length (in bytes; may be odd) of UTF-16LE buffer.
>> + *
>> + * Return: The number of bytes filled in: 2*strlen(s) or @len,
>> whichever is less
>> + */
>> +unsigned int ascii2utf16le(char const *s, u8 *buf, unsigned int len)
>> +{
>> +    unsigned int n, t = 2 * strlen(s);
>> +
>> +    if (len > t)
>> +        len = t;
>> +    n = len;
>> +    while (n--) {
>> +        t = (unsigned char)*s++;
>> +        *buf++ = t;
>> +        if (!n--)
>> +            break;
>> +        *buf++ = t >> 8;
> 
>    Isn't it always 0?

As I will remove this function and use utf8s_to_utf16s() instead (as
suggested by Alan Stern) IMHO this issue needs no more attention.

Nonetheless, thank you for your feedback!

> 
>> +    }
>> +    return len;
>> +}
>> +EXPORT_SYMBOL(ascii2utf16le);

regards,
Richard L