From: Johan Hovold <johan@kernel.org>
To: linux-usb@vger.kernel.org
Cc: Johan Hovold <johan@kernel.org>
Subject: [PATCH] USB: serial: ftdi_sio: restore divisor-encoding comments
Date: Wed, 27 Jan 2021 12:00:28 +0100 [thread overview]
Message-ID: <20210127110028.5127-1-johan@kernel.org> (raw)
Add back a few explanatory comments related to the divisor encoding
which got lost in a coding-style clean up many years ago.
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/usb/serial/ftdi_sio.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 94398f89e600..a6837a60c06a 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1153,13 +1153,13 @@ static unsigned short int ftdi_232am_baud_base_to_divisor(int baud, int base)
divisor = divisor3 >> 3;
divisor3 &= 0x7;
if (divisor3 == 1)
- divisor |= 0xc000;
+ divisor |= 0xc000; /* +0.125 */
else if (divisor3 >= 4)
- divisor |= 0x4000;
+ divisor |= 0x4000; /* +0.5 */
else if (divisor3 != 0)
- divisor |= 0x8000;
+ divisor |= 0x8000; /* +0.25 */
else if (divisor == 1)
- divisor = 0; /* special case for maximum baud rate */
+ divisor = 0; /* special case for maximum baud rate */
return divisor;
}
@@ -1177,9 +1177,9 @@ static u32 ftdi_232bm_baud_base_to_divisor(int baud, int base)
divisor = divisor3 >> 3;
divisor |= (u32)divfrac[divisor3 & 0x7] << 14;
/* Deal with special cases for highest baud rates. */
- if (divisor == 1)
+ if (divisor == 1) /* 1.0 */
divisor = 0;
- else if (divisor == 0x4001)
+ else if (divisor == 0x4001) /* 1.5 */
divisor = 1;
return divisor;
}
@@ -1201,9 +1201,9 @@ static u32 ftdi_2232h_baud_base_to_divisor(int baud, int base)
divisor = divisor3 >> 3;
divisor |= (u32)divfrac[divisor3 & 0x7] << 14;
/* Deal with special cases for highest baud rates. */
- if (divisor == 1)
+ if (divisor == 1) /* 1.0 */
divisor = 0;
- else if (divisor == 0x4001)
+ else if (divisor == 0x4001) /* 1.5 */
divisor = 1;
/*
* Set this bit to turn off a divide by 2.5 on baud rate generator
--
2.26.2
reply other threads:[~2021-01-27 11:15 UTC|newest]
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