From: Robin Murphy > Sent: 08 April 2019 11:24 > On 07/04/2019 05:31, Sai Prakash Ranjan wrote: > > On 4/5/2019 6:44 PM, David Laight wrote: > >> From: Sai Prakash Ranjan > >>> > >>> diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c > >>> index 93ce3aa740a9..21a5838f6e67 100644 > >>> --- a/drivers/hwtracing/stm/core.c > >>> +++ b/drivers/hwtracing/stm/core.c > >>> @@ -168,7 +168,7 @@ static int stp_master_alloc(struct stm_device > >>> *stm, unsigned int idx) > >>> struct stp_master *master; > >>> size_t size; > >>> > >>> - size = ALIGN(stm->data->sw_nchannels, 8) / 8; > >>> + size = ALIGN(stm->data->sw_nchannels, STM_MASTER_SZ) / > >>> STM_MASTER_SZ; > >> > >> I'm not sure that using STP_MASTER_SZ improves readability at all. > >> > > > > I thought it was better to have a macro than directly specifying > > sizeof(unsigned long), anyways I can change it. > > > >> Is there something that gives the size of a bitmap for 'n' items? > >> > > > > Not sure if there is something. > > If you were to ask the question "how does the bitmap code itself know > what the total size of a bitmap is?", that would quickly lead you > towards BITS_TO_LONGS() ;) > > And given that stp_master::chan_map is already an appropriate type, that > suggests simplifying the entire calculation down to something neat and > tidy like: > > size = offsetof(struct stp_master, chan_map[BITS_TO_LONGS(stm->data->sw_nchannels)]); Except that is invalid. You can't use offsetof() with something that isn't a compile time constant. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
