diff options
Diffstat (limited to 'drivers/usb/mon/mon_bin.c')
| -rw-r--r-- | drivers/usb/mon/mon_bin.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/drivers/usb/mon/mon_bin.c b/drivers/usb/mon/mon_bin.c index afb71c18415d..e713fc5964b1 100644 --- a/drivers/usb/mon/mon_bin.c +++ b/drivers/usb/mon/mon_bin.c @@ -68,18 +68,20 @@ * The magic limit was calculated so that it allows the monitoring * application to pick data once in two ticks. This way, another application, * which presumably drives the bus, gets to hog CPU, yet we collect our data. - * If HZ is 100, a 480 mbit/s bus drives 614 KB every jiffy. USB has an - * enormous overhead built into the bus protocol, so we need about 1000 KB. + * + * Originally, for a 480 Mbit/s bus this required a buffer of about 1 MB. For + * modern 20 Gbps buses, this value increases to over 50 MB. The maximum + * buffer size is set to 64 MiB to accommodate this. * * This is still too much for most cases, where we just snoop a few * descriptor fetches for enumeration. So, the default is a "reasonable" - * amount for systems with HZ=250 and incomplete bus saturation. + * amount for typical, low-throughput use cases. * * XXX What about multi-megabyte URBs which take minutes to transfer? */ -#define BUFF_MAX CHUNK_ALIGN(1200*1024) -#define BUFF_DFL CHUNK_ALIGN(300*1024) -#define BUFF_MIN CHUNK_ALIGN(8*1024) +#define BUFF_MAX CHUNK_ALIGN(64*1024*1024) +#define BUFF_DFL CHUNK_ALIGN(300*1024) +#define BUFF_MIN CHUNK_ALIGN(8*1024) /* * The per-event API header (2 per URB). @@ -823,7 +825,7 @@ static ssize_t mon_bin_read(struct file *file, char __user *buf, ep = MON_OFF2HDR(rp, rp->b_out); if (rp->b_read < hdrbytes) { - step_len = min(nbytes, (size_t)(hdrbytes - rp->b_read)); + step_len = min_t(size_t, nbytes, hdrbytes - rp->b_read); ptr = ((char *)ep) + rp->b_read; if (step_len && copy_to_user(buf, ptr, step_len)) { mutex_unlock(&rp->fetch_lock); |