[PATCH libbsd] mmcsd: Fix missing MMCBUS_RELEASE_BUS.

[Sebastian Huber]

On 01/04/2020 10:41, Sebastian Huber wrote:

>>         for (i = 0; i < buffer_count; ++i) {
>> @@ -394,6 +399,7 @@ rtems_bsd_mmcsd_disk_read_write(struct mmcsd_part 
>> *part, rtems_blkdev_request *b
>>   error:
>>         MMCSD_DISK_UNLOCK(part);
>> +    MMCBUS_RELEASE_BUS(device_get_parent(dev), dev);
>>         rtems_blkdev_request_done(blkreq, status_code);
>>   @@ -436,8 +442,6 @@ rtems_bsd_mmcsd_attach_worker(rtems_media_state 
>> state, const char *src, char **d
>>               goto error;
>>           }
>>   -        MMCBUS_ACQUIRE_BUS(device_get_parent(dev), dev);
>
> I think the bus acquire here is necessary to prevent an 
> rtems_blkdev_create() while the bus is detached in parallel, e.g. a 
> fast plug/unplug of an USB stick.
Sorry, this comment makes little sense, this code is not for USB sticks. 
However, if we want to support hot plugging of MMC busses and devices, 
then the rtems_blkdev_create() during a concurrent detach is something 
we have to consider.
>
> After reviewing the code I think this bus acquire without a release 
> (which is in the code since the import from libusb in 2015) was a hack 
> to improve the read/write performance. We didn't support hot plugging 
> of MMC busses and devices. Do we need this feature now? 

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