Re: [PATCH v3 4/5] usb: gadget: mass_storage: Use static array for luns

[Michal Nazarewicz <mina86@mina86.com>]

> On 07/08/2015 04:00 PM, Michal Nazarewicz wrote:
>> On Tue, Jul 07 2015, Krzysztof Opasiak wrote:
>>> This patch replace dynamicly allocated luns array with static one.
>>> This simplifies the code of mass storage function and modules.
>>>
>>> It also fix issue with reporting wrong number of LUNs in GET_MAX_LUN
>>> request. According to MS spec we should return the max index of valid
>>> LUN, not the number of luns - 1.
>>
>> This is no longer true, is it?  Why my fix this bug has been solved, no?
>> As such, this should not go to stable.  Or am I missing something?

On Mon, Jul 20 2015, Krzysztof Opasiak wrote:
> Unfortunately it's still true. Your fix solved this bug partially. Now 
> we report nluns - 1 instead of FSG_LUN_MAX but in case of not contiguous 
> luns it is not enough.
>
> Let's consider mass storage function with luns 0 1 3 5. nluns == 4 so in 
> GET_MAX_LUN we will return 3 (nluns - 1).

I don’t believe that’s accurate.  See loop in my patch:

+       if (!opts->refcnt) {
+               for (nluns = i = 0; i < FSG_MAX_LUNS; ++i)
+                       if (common->luns[i])
+                               nluns = i + 1;
+               if (!nluns)
+                       pr_warn("No LUNS defined, continuing anyway\n");
+               else
+                       common->nluns = nluns;
+               pr_info("Number of LUNs=%u\n", common->nluns);
+       }

It iterates over all luns and if lun is non-NULL it sets nluns to index
of that lun plus one.  So if luns[0], lun[1], lun[2], lun[3] and lun[5]
are set, common->nluns = 6.

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