-----Original Message----- From: york sun Sent: Tuesday, January 26, 2016 1:02 AM To: Scott Wood scott.wood@nxp.com; Yao Yuan yao.yuan@nxp.com; Qianyu Gong qianyu.gong@nxp.com Cc: B48286@freescale.com; u-boot@lists.denx.de; Wenbin.Song@freescale.com; jteki@openedev.com Subject: Re: [U-Boot] [Patch V5 2/4] spi: fsl_qspi: Fix qspi_op_rdid memcpy issue
On 01/25/2016 09:01 AM, Scott Wood wrote:
On 01/25/2016 10:47 AM, york sun wrote:
On 01/24/2016 08:09 PM, Yao Yuan wrote:
On 01/25/2016 04:16 AM, York Sun wrote:
On 01/22/2016 07:43 AM, Scott Wood wrote:
On 01/21/2016 09:35 PM, Qianyu Gong wrote: > >> -----Original Message----- >> From: Scott Wood >> Sent: Friday, January 22, 2016 3:30 AM >> To: Qianyu Gong qianyu.gong@nxp.com; u-boot@lists.denx.de; >> R58495@freescale.com >> Cc: Mingkai.Hu@freescale.com; jteki@openedev.com; >> B48286@freescale.com; Shaohui.Xie@freescale.com; >> Wenbin.Song@freescale.com; Scott Wood oss@buserror.net; Gong >> Qianyu Qianyu.Gong@freescale.com >> Subject: Re: [Patch V5 2/4] spi: fsl_qspi: Fix qspi_op_rdid >> memcpy issue >> >> On 01/20/2016 09:43 PM, Gong Qianyu wrote: >>> From: Gong Qianyu Qianyu.Gong@freescale.com >>> >>> In current driver everytime we memcpy 4 bytes to the dest >>> memory regardless of the remaining length. >>> This patch adds checking the remaining length before memcpy. >>> If the length is shorter than 4 bytes, memcpy the actual length >>> of data to the dest memory. >>> >>> Signed-off-by: Gong Qianyu Qianyu.Gong@freescale.com >>> --- >>> V2-V5: >>> - No change. >>> >>> drivers/spi/fsl_qspi.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/spi/fsl_qspi.c b/drivers/spi/fsl_qspi.c >>> index >>> 38e5900..f178857 100644 >>> --- a/drivers/spi/fsl_qspi.c >>> +++ b/drivers/spi/fsl_qspi.c >>> @@ -500,7 +500,10 @@ static void qspi_op_rdid(struct >>> fsl_qspi_priv *priv, u32 >> *rxbuf, u32 len) >>> if (rbsr_reg & QSPI_RBSR_RDBFL_MASK) { >>> data = qspi_read32(priv->flags, ®s->rbdr[i]); >>> data = qspi_endian_xchg(data); >>> - memcpy(rxbuf, &data, 4); >>> + if (size < 4) >>> + memcpy(rxbuf, &data, size); >>> + else >>> + memcpy(rxbuf, &data, 4); >> >> memcpy(rxbuf, &data, min(size, 4)); >> >>> rxbuf++; >>> size -= 4; >>> i++; >> >> size -= 4 even if size was < 4? >> >> -Scott > > Yes.. The following is complete code: > > i = 0; > size = len; > while ((RX_BUFFER_SIZE >= size) && (size > 0)) { > rbsr_reg = qspi_read32(priv->flags, ®s->rbsr); > if (rbsr_reg & QSPI_RBSR_RDBFL_MASK) { > data = qspi_read32(priv->flags, ®s->rbdr[i]); > data = qspi_endian_xchg(data); > memcpy(rxbuf, &data, min(size, 4)); > rxbuf++; > size -= 4; > i++; > } > }
I'm not saying it doesn't work (assuming i is signed, which the "complete code" above doesn't show). I'm saying it looks weird, and it would be better to have a variable that holds min(size, 4) and pass that to both memcpy and the subtraction.
Qianyu,
Previously I said it looked weird for doing this. Please fix.
"size" is declared as "int". "len" is declared as u32. That's not "int". If you trace back the functions, you may see it came from DIV_ROUND_UP(bitlen, 8) where bitlen
is "unsigned int".
So technically the code is safe. But it is _confusing_. We don't want to confuse ourselves when reading the code later. And the fix is easy,
isn't it?
York
How about like this?
diff --git a/drivers/spi/fsl_qspi.c b/drivers/spi/fsl_qspi.c index feec3e8..13bba09 100644 --- a/drivers/spi/fsl_qspi.c +++ b/drivers/spi/fsl_qspi.c @@ -477,8 +477,8 @@ static void qspi_op_rdbank(struct fsl_qspi_priv *priv, u8 *rxbuf, u32 len) static void qspi_op_rdid(struct fsl_qspi_priv *priv, u32 *rxbuf, u32 len) { struct fsl_qspi_regs *regs = priv->regs;
u32 mcr_reg, rbsr_reg, data;int i, size;
u32 mcr_reg, rbsr_reg, data, size;int i; mcr_reg = qspi_read32(priv->flags, ®s->mcr); qspi_write32(priv->flags, ®s->mcr, @@ -495,14 +495,14 @@static void qspi_op_rdid(struct fsl_qspi_priv *priv, u32 *rxbuf, u32 len)
i = 0; size = len;
while ((RX_BUFFER_SIZE >= size) && (size > 0)) {
while ((RX_BUFFER_SIZE >= size) && (size != 0)) {You can keep using "size > 0". It is still correct.
And more robust.
rbsr_reg = qspi_read32(priv->flags, ®s->rbsr); if (rbsr_reg & QSPI_RBSR_RDBFL_MASK) { data = qspi_read32(priv->flags, ®s->rbdr[i]); data = qspi_endian_xchg(data);
memcpy(rxbuf, &data, 4);
memcpy(rxbuf, &data, min(size, 4));size = (size < 4) ? 0 : ( size - 4); rxbuf++;
size -= 4; i++; } }The rest looks OK to me.
It's still awkward compared to:
int chunk;
...
chunk = min(size, 4); memcpy(rxbuf, &data, chunk); size -= chunk;
Agree.
York
Great. Thank you all. I send out a V7 patch set to fix it.
Regards, Qianyu